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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenTue, 16 Apr 2024 15:17:02 +0000High-Energy Nucleon Compton Scattering
https://resolver.caltech.edu/CaltechETD:etd-05022005-142830
Authors: {'items': [{'id': 'Zmuidzinas-Jonas-Stasys', 'name': {'family': 'Zmuidzinas', 'given': 'Jonas Stasys'}, 'show_email': 'NO'}]}
Year: 1963
DOI: 10.7907/ZV5K-YT46
The high-energy nucleon Compton scattering process is studied to second order in the electromagnetic coupling constant from the viewpoint of complex angular momenta. Assuming the validity of the Regge hypothesis about the asymptotic behavior of scattering amplitudes, formulae for total and differential cross sections in the forward and backward directions are derived. Residues of Regge poles in their physical regions are estimated on the basis of existing experimental data. The implications of possible Regge cuts are discussed.
https://thesis.library.caltech.edu/id/eprint/1576Regge Poles in Field Theories and Elementarity
https://resolver.caltech.edu/CaltechETD:etd-09112002-174326
Authors: {'items': [{'id': 'Chester-Arthur-Noble', 'name': {'family': 'Chester', 'given': 'Arthur Noble'}, 'show_email': 'NO'}]}
Year: 1965
DOI: 10.7907/4VEV-4D57
<p>It is known that in the field theory description of the Compton scattering of nucleons by vector mesons the nucleon lies on a Regge trajectory. In this work it is found that the vector meson channel of the same theory exhibits no such Regge-like behavior. However, in electron-graviton scattering the spinor particle is again Reggeized.</p>
<p>The various problems that arise when zero mass mesons are used in the scattering are discussed and it is shown that the Reggeization generally proceeds as in the massive case. A field theory of massive gravitons is discussed.</p>
<p>The dynamical criterion of vanishing renormalization constants is applied to Reggeized particles and it is shown that this criterion successfully distinguishes an elementary Reggeized particle from a true dynamical state. This provides a dynamical test which can replace the postulate that a "bootstrapped" theory is characterized by the absence of Kronecker delta terms in all channels. We may thus recover the one-to-one correspondence between dynamical particles and certain moving poles in the partial wave amplitudes.</p>
<p>Appendices B and C review the generation of Regge trajectories by iteration through unitarity and Mandelstam's treatment of Reggeization using the N/D equations.</p>https://thesis.library.caltech.edu/id/eprint/3453A Study of T = 1, T = 3/2, and T = 2 States in Some Light Nuclei Using (He³,n) Reactions
https://resolver.caltech.edu/CaltechTHESIS:11022015-134907826
Authors: {'items': [{'id': 'Adelberger-Eric-George', 'name': {'family': 'Adelberger', 'given': 'Eric George'}, 'show_email': 'NO'}]}
Year: 1967
DOI: 10.7907/D6GW-RW22
<p>The (He<sup>3</sup>, n) reactions on B<sup>11</sup>, N<sup>15</sup>, O<sup>16</sup>, and O<sup>18</sup> targets have been studied using a pulsed-beam time-of-flight spectrometer. Special emphasis was placed upon the determination of the excitation energies and properties of states with T = 1 (in Ne<sup>18</sup>), T = 3/2 (in N<sup>13</sup> and F<sup>17</sup>) and T = 2 (in Ne<sup>20</sup>). The identification of the T = 3/2 and T = 2 levels is based on the structure of these states as revealed by intensities and shapes of angular distributions. The reactions are interpreted in terms of double stripping theory. Angular distributions have been compared with plane and distorted wave stripping theories. Results for the four reactions are summarized below: </p>
<p>1) O<sup>16</sup> (He<sup>3</sup>, n). The reaction has been studied at incident energies up to 13.5 MeV and two previously unreported levels in Ne<sup>18</sup> were observed at E<sub>x</sub> = 4.55 ± .015 MeV (Γ = 70 ± 30 keV) and E<sub>x</sub> = 5.14 ± .018 MeV (Γ = 100 ± 40 keV).</p>
<p>2) B<sup>11</sup> (He<sup>3</sup>, n). The reaction has been studied at incident energies up to 13.5 MeV. Three T = 3/2 levels in N<sup>13</sup> have been identified at E<sub>x</sub> = 15.068 ± .008 MeV (Γ ˂ 15 keV), E<sub>x</sub> = 18.44 ± .04, and E<sub>x</sub> 18.98 ± .02 MeV (Γ = 40 ± 20 keV).</p>
<p>3) N<sup>15</sup> (He<sup>3</sup>, n). The reaction has been studied at incident energies up to 11.88 MeV. T = 3/2 levels in F<sup>17</sup> have been identified at E<sub>x</sub> = 11.195 ± .007 MeV (Γ ˂ 20 keV), E<sub>x</sub> = 12.540 ± .010 MeV (Γ ˂ 25 keV), and E<sub>x</sub> = 13.095 ± .009 MeV (Γ ˂ 25 keV). </p>
<p>4) O<sup>18</sup> (He<sup>3</sup>, n). The reaction has been studied at incident energies up to 9.0 MeV. The excitation energy of the lowest T = 2 level in Ne<sup>20</sup> has been found to be 16.730 ± .006 MeV (Γ ˂ 20 keV). </p>
<p>Angular distributions of the transitions leading to the above higher isospin states are well described by double stripping theory. Analog correspondences are established by comparing the present results with recent studies (t, p) and (He<sup>3</sup>, p) reactions on the same targets. </p>
https://thesis.library.caltech.edu/id/eprint/9267A relativistic quark model with harmonic dynamics
https://resolver.caltech.edu/CaltechETD:etd-05022005-085218
Authors: {'items': [{'id': 'Ravndal-F', 'name': {'family': 'Ravndal', 'given': 'Finn'}, 'show_email': 'NO'}]}
Year: 1971
DOI: 10.7907/XRTB-V265
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
A relativistic equation to represent the symmetric quark model of hadrons with harmonic interaction is constructed. This gives straight and parallel Regge trajectories and a hadron spectrum which easily can accommodate all known resonances. From the equation we derive vector and axial vector currents for baryons and mesons. The vector current matrix elements of baryons are compared to known magnetic moments, photoproduction amplitudes and inelastic electron proton cross sections. Good agreement is obtained when the theoretical results are modified by an empirical form factor. Besides this form factor, the results depend on no free parameters. Using the same form factor, we calculate radiative decay rates of vector mesons and parameters of K[...] decay, which agree fairly well with experiment. Assuming that the amplitude for emission of a pseudoscalar meson from a hadron is proportional to the divergence of the axial vector current, we calculate most of the known strong decay rates. These results depend on one new coupling constant and a smooth, empirical form factor. More than half of the calculated baryon rates agree well with experiment. The reasons for the many disagreements are discussed. All except one of the meson rates come out close to their experimental values. The angular distributions of the decay B(1235) [...] and A[...](1070) [...] are well described in this model.
https://thesis.library.caltech.edu/id/eprint/1574Stability and supersymmetry
https://resolver.caltech.edu/CaltechETD:etd-12092004-161650
Authors: {'items': [{'email': 'curtright@physics.miami.edu', 'id': 'Curtright-T-L', 'name': {'family': 'Curtright', 'given': 'Thomas Lynn'}, 'show_email': 'NO'}]}
Year: 1977
DOI: 10.7907/X6XZ-AX26
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
PART I
A complete account of a perturbative investigation of ground state instability is presented for a massless theory involving scalar, pseudoscalar, and Majorana spinor fields. The effective potential, dimensional regularization, and renormalization group formalisms are briefly reviewed and then applied in detail to show the semiclassical vacuum of the model is unstable due to radiative corrections when the (pseudo)scalar self-interaction strength, f, is less than the fermion-(pseudo)scalar coupling, [...]. Models with stable ground states are found when [...], and when [...] supersymmetric theory is obtained. The supersymmetric case is thus encountered as a boundary between stable and unstable models. This result is discussed and is conjectured to be a general feature of supersymmetric theories. All perturbative calculations in the analysis are methodically carried out to the level of two-loop Feynman diagrams, and to this level, a variety of renormalization prescriptions are considered. The correlation of the various ultraviolet divergences for the supersymmetric model is explicitly demonstrated and shown not to hold in the general theory.
PART II
Renormalization group analysis is used to show the supersymmetric point in the effective coupling constant space is an unstable fixed point for several model gauge theories. The physical significance of this result is discussed in terms of the stability of the semiclassical ground state. In perturbation theory the supersymmetric point appears to be surrounded by regions in the coupling space representing three classes of theories: class one consists of theories for which the effective potential V has no apparent lower bound for large (pseudo) scalar field expectations; class two theories have lower bounds and radiatively induced absolute minima for V with nonzero field expectations; class three theories apparently have an absolute minimum of V at the origin of field space. Thus radiatively induced breaking of gauge invariance occurs for theories in classes one and two, but perturbatively the class one theories appear to have no ground states. Class three theories have ground states in which all gauge invariance remains intact. For the supersymmetric limits of the models examined the origin is known to be neutrally stable in field space, permitting an ambiguous breakdown of gauge invariance but not supersymmetry. This phenomenon is discussed in some detail. Calculations are performed in both Lorentz covariant and noncovariant gauges with a detailed comparison between gauges of the relevant one-loop diagrams. A null-plane limit of the noncovariant gauges is argued not to exist.
https://thesis.library.caltech.edu/id/eprint/4898Some Topics in Theoretical High-Energy Physics
https://resolver.caltech.edu/CaltechETD:etd-06142007-142536
Authors: {'items': [{'id': 'Wolfram-Stephen', 'name': {'family': 'Wolfram', 'given': 'Stephen'}, 'show_email': 'NO'}]}
Year: 1980
DOI: 10.7907/S6JE-QF83
This thesis discusses various aspects of theoretical high-energy physics. The first two sections describe methods for investigating QCD effects in e⁺e⁻ annihilation to hadrons. The third section presents some predictions for various features of QCD jets. The fourth section shows that any fermions in the standard weak interaction model must have masses ≾100 GeV. In the fifth section, the abundances of any new absolutely stable heavy particles which should have been produced in the early universe are estimated, and found to be inconsistent with observational limits. Finally, the sixth section describes the development of a baryon excess in the very early universe due to B, CP violating interactions.
https://thesis.library.caltech.edu/id/eprint/2597Baryon Number Generation and Mass Relations in SO(10) Unified Models
https://resolver.caltech.edu/CaltechTHESIS:01302018-144721271
Authors: {'items': [{'id': 'Harvey-Jeffrey-Alan', 'name': {'family': 'Harvey', 'given': 'Jeffrey Alan'}}]}
Year: 1981
DOI: 10.7907/mv0x-zk52
<p>Two topics are discussed in this thesis. The first is the calculation of cosmological baryon number generation in the early universe. These calculations are performed for a variety of SU(5) and SO(10) unified models. The effects of superheavy fermions and charge conjugation symmetry are discussed in the context of SO(10) models. The second section contains an analysis of natural fermion mass and mixing angle relations in a grand unified model based on SO(10). These relations are used to study neutrino masses and oscillations. Appreciable mixing is found only between μ and τ neutrinos. Spinor representations of the Lorentz group and of SO(10) are described in two appendices.</p>https://thesis.library.caltech.edu/id/eprint/10657General Methods for Analyzing Higgs Potentials
https://resolver.caltech.edu/CaltechTHESIS:07122018-154521178
Authors: {'items': [{'email': 'jsk@postech.ac.kr', 'id': 'Kim-Jai-Sam', 'name': {'family': 'Kim', 'given': 'Jai Sam'}, 'show_email': 'YES'}]}
Year: 1982
DOI: 10.7907/RAFF-A683
<p>This thesis is based on several papers published by the author and some more work to be published. We explain the technical problem of minimizing Higgs potentials using group theoretical concepts. Three mathematical results which belong to distinct areas are used to analyze the Higgs potential in an abstract way. The problem reduces to one of finding "contours" of directional minima and thus our method is geometrical. It is explained in detail and demonstrated for some simple cases. We show that the Michel-Radicati conjecture and the Gell-Mann-Slansky conjecture have geometrical significance besides predicting the most likely symmetry groups of the absolute minimum of the potential. We also apply the method to a non-monotonic potential.</p>https://thesis.library.caltech.edu/id/eprint/11118Erosion of Ice Films by Energetic Ions
https://resolver.caltech.edu/CaltechTHESIS:04182018-111515439
Authors: {'items': [{'id': 'Cooper-Barbara-Hope', 'name': {'family': 'Cooper', 'given': 'Barbara Hope'}}]}
Year: 1982
DOI: 10.7907/yyye-qc47
<p>We measured the sputtering yields of ice films by <sup>19</sup>F ions in the electronic stopping power energy regime. The yield was a function of the incident energy and charge state of the F beam, but did not vary for target thicknesses ranging from about 30-70 x 10<sup>16</sup>H<sub>2</sub>O/cm<sup>2</sup>, or substrate temperatures from 10-60°K.</p>
<p>The energy dependence of the yield demonstrates that the sputtering mechanism is related to the electronic stopping power of the incident ion in the ice film. The detailed nature of this dependence is not understood. Predictions of thermal models and ion explosion models are compared to the experimental results.</p>
<p>Our F data on ice is compared to H and He sputtering of ice. We also review results from the literature where sputtering of other dielectric targets with ions in the electronic stopping power regime have been studied.</p>
<p>Possible connections with nuclear track formation in dielectrics and laser annealing are discussed. We also briefly mention the applications of enhanced sputtering of dielectrics; for example, in non-destructive desorption of large biomolecules and in astrophysical environments where frozen gas surf aces are bombarded by energetic ion fluxes.</p>
https://thesis.library.caltech.edu/id/eprint/10816Phase Conjugation via Four-Wave Mixing in a Resonant Medium
https://resolver.caltech.edu/CaltechTHESIS:02182014-143316560
Authors: {'items': [{'email': 'nilsen1@llnl.gov', 'id': 'Nilsen-Joseph-Michael', 'name': {'family': 'Nilsen', 'given': 'Joseph Michael'}, 'show_email': 'YES'}]}
Year: 1982
DOI: 10.7907/RV9B-GV44
<p>This thesis describes the theoretical solution and experimental verification of phase conjugation via nondegenerate four-wave mixing in resonant media. The theoretical work models the resonant medium as a two-level atomic system with the lower state of the system being the ground state of the atom. Working initially with an ensemble of stationary atoms, the density matrix equations are solved by third-order perturbation theory in the presence of the four applied electro-magnetic fields which are assumed to be nearly resonant with the atomic transition. Two of the applied fields are assumed to be non-depleted counterpropagating pump waves while the third wave is an incident signal wave. The fourth wave is the phase conjugate wave which is generated by the interaction of the three previous waves with the nonlinear medium. The solution of the density matrix equations gives the local polarization of the atom. The polarization is used in Maxwell's equations as a source term to solve for the propagation and generation of the signal wave and phase conjugate wave through the nonlinear medium. Studying the dependence of the phase conjugate signal on the various parameters such as frequency, we show how an ultrahigh-Q isotropically sensitive optical filter can be constructed using the phase conjugation process.</p>
<p>In many cases the pump waves may saturate the resonant medium so we also present another solution to the density matrix equations which is correct to all orders in the amplitude of the pump waves since the third-order solution is correct only to first-order in each of the field amplitudes. In the saturated regime, we predict several new phenomena associated with degenerate four-wave mixing and also describe the ac Stark effect and how it modifies the frequency response of the filtering process. We also show how a narrow bandwidth optical filter with an efficiency greater than unity can be constructed.</p>
<p>In many atomic systems the atoms are moving at significant velocities such that the Doppler linewidth of the system is larger than the homogeneous linewidth. The latter linewidth dominates the response of the ensemble of stationary atoms. To better understand this case the density matrix equations are solved to third-order by perturbation theory for an atom of velocity v. The solution for the polarization is then integrated over the velocity distribution of the macroscopic system which is assumed to be a gaussian distribution of velocities since that is an excellent model of many real systems. Using the Doppler broadened system, we explain how a tunable optical filter can be constructed whose bandwidth is limited by the homogeneous linewidth of the atom while the tuning range of the filter extends over the entire Doppler profile.</p>
<p>Since it is a resonant system, sodium vapor is used as the nonlinear medium in our experiments. The relevant properties of sodium are discussed in great detail. In particular, the wavefunctions of the 3S and 3P states are analyzed and a discussion of how the 3S-3P transition models a two-level system is given.</p>
<p>Using sodium as the nonlinear medium we demonstrate an ultrahigh-Q optical filter using phase conjugation via nondegenerate four-wave mixing as the filtering process. The filter has a FWHM bandwidth of 41 MHz and a maximum efficiency of 4 x 10<sup>-3</sup>. However, our theoretical work and other experimental work with sodium suggest that an efficient filter with both gain and a narrower bandwidth should be quite feasible.</p>
https://thesis.library.caltech.edu/id/eprint/8081Pion-Pion Decay Distributions for π⁻p → π⁺π⁻n at 100 and 175 GeV/c
https://resolver.caltech.edu/CaltechTHESIS:05172018-112232901
Authors: {'items': [{'id': 'Stampke-Stuart-Reh', 'name': {'family': 'Stampke', 'given': 'Stuart Reh'}, 'show_email': 'NO'}]}
Year: 1982
DOI: 10.7907/bfmr-3581
<p>We report measurements of the reaction π<sup>-</sup>p → π<sup>+</sup>π<sup>-</sup>n at 100 and 175 GeV/c using a large wire chamber spectrometer at Fermilab. Production of <i>ρ</i><sup>0</sup>, <i>f</i><sup>0</sup>, and <i>g</i><sup>0</sup> resonances was observed. Cross sections for π<sup>-</sup>p → π<sup>+</sup>π<sup>-</sup>n in the <i>ρ</i><sup>0</sup> mass region are given. Decay angle distributions for ππ masses from .55 to 3.5 GeV/c<sup>2</sup> are presented. Moment analyses of the decay distributions are made as a function of ππ mass from .55 to 2.4 GeV/c<sup>2</sup>. Contours of ππ decay distribution dips are given in <i>s</i><sub>ππ</sub> and <i>t</i><sub>ππ</sub>. Comparisons with several lower energy experiments are made. Detailed discussions of the apparatus, trigger, and analysis procedures are given.</p>https://thesis.library.caltech.edu/id/eprint/10911Semiclassical Quantization in Many Dimensions
https://resolver.caltech.edu/CaltechTHESIS:10312019-103914805
Authors: {'items': [{'id': 'Williams-Roy-David', 'name': {'family': 'Williams', 'given': 'Roy David'}, 'show_email': 'NO'}]}
Year: 1983
DOI: 10.7907/ezwt-k047
<p>We examine the semiclassical limit of the quantum energy spectrum in many dimensions: by means of a WKB-like ansatz leading to Einstein-Brillouin-Keller (EBK) quantization, by means of a path integral, hence associating a bound state with a particular classical periodic trajectory, and by the Birkhoff-Gustavson (BG) transformation to action-angle variables. We extend the EBK method to many-fermion systems using coherent states; and apply both EBK using surfaces of section, and the BG transformation to an SU(3) schematic nuclear shell model. We describe a new algorithm for finding periodic trajectories of a Lagrangian system with polynomial potential. It is applied to the Henon-Heiles system with good results, and these trajectories are used to quantize the system. The EBK and BG methods have some success, while periodic trajectory quantization fails. We discuss possible reasons for this failure and future approaches to these problems.</p>https://thesis.library.caltech.edu/id/eprint/11876Topics in Grand Unified Theories: i) The Naturalness Problem. ii) Monopoles and Fermion Number Violation
https://resolver.caltech.edu/CaltechTHESIS:10232019-171800698
Authors: {'items': [{'id': 'Sathiapalan-Balachandran', 'name': {'family': 'Sathiapalan', 'given': 'Balachandran'}, 'show_email': 'NO'}]}
Year: 1983
DOI: 10.7907/m0cj-7n28
<p>This dissertation consists of two parts. The first part contains a discussion of the 'fine-tuning' and 'naturalness ' problems in grand unified theories. It is argued that, while it is impossible to solve these problems in conventional theories which contain scalars, supersymmetric theories that require no fine tuning can be constructed. In these theories the problem reduces to that of obtaining a light Higgs doublet at the tree level, without any unnatural adjustment of parameters. A realistic supersymmetric grand unified theory that has this feature is constructed. It is based on the gauge group SO(10). Supersymmetry is explicitly broken through terms of dimension two.</p>
<p>The second part is an analysis of the interaction of fermions with a non-Abelian ('t Hooft-Polyakov) monopole. Monopoles are invariably present in grand unified theories, and recent studies with massless isospin half fermions have shown that monopoles catalyse fermion number violation. We show that this phenomenon can be described in simple terms using the language of instanton physics. This description also permits a straightforward extension of previous results to arbitrary fermion representations. The importance of half-integer winding numbers is stressed. An explicit calculation is done in the case of isovector fermions.</p>https://thesis.library.caltech.edu/id/eprint/11854Radiative Mass Structure in Unified Models and Fermions in the Desert
https://resolver.caltech.edu/CaltechTHESIS:09272018-120912826
Authors: {'items': [{'id': 'Bowick-Mark-John', 'name': {'family': 'Bowick', 'given': 'Mark John'}, 'show_email': 'NO'}]}
Year: 1983
DOI: 10.7907/11jn-dn31
<p>The radiative mass structure of some Grand Unified Models is discussed. They contain fermions with SU(2)-invariant masses in the desert. The possibility of such fermions is examined in detail with the conclusion that their mass can be low enough (~ 20 GeV) to be found in accelerators today. The mixing of such fermions with ordinary fermions is analysed and their contribution to rare processes calculated. They do not upset standard GUT predictions. Finally an analysis of their contribution to the μ → eγ rate is an interesting illustration of decoupling.</p>https://thesis.library.caltech.edu/id/eprint/11206A Leading Order QCD Computation of ππ Elastic Scattering
https://resolver.caltech.edu/CaltechTHESIS:10172019-165231405
Authors: {'items': [{'id': 'Kanwal-Sarbmeet-Singh', 'name': {'family': 'Kanwal', 'given': 'Sarbmeet Singh'}, 'show_email': 'NO'}]}
Year: 1983
DOI: 10.7907/7xbf-c510
<p>This thesis presents the results of a detailed computation of the leading order scattering amplitude and cross-section for the elastic reaction π<sup>+</sup>π<sup>+</sup> → π<sup>+</sup>π<sup>+</sup>, in the context of the quark model and perturbative QCD. The calculation is based on the recently demonstrated applicability of QCD-factorization and the renormalization group to exclusive hadronic processes at large momentum-transfers. We show that a large fraction of the hard subprocess diagrams have a pinch singularity in them, which means that the amplitude resulting from these diagrams cannot be proved to be short-distance dominated. This contribution to the scattering amplitude is computed separately and, even after including a Sudakov factor, it is shown to be comparable in magnitude to the hard-scattering contribution. We calculate the energy and angular dependence of the pinch contribution and point out that some of the systematic deviations from power-law scaling, observed in high-P<sub>T</sub> meson-baryon and baryon-baryon elastic scattering data, can be explained by assuming that the cross-section for these reactions is dominated by pinch, rather than hard, effects. By normalizing the pion distribution amplitude with the help of the pion decay constant, we have also determined the absolute normalization of the ππ elastic cross-section.</p>https://thesis.library.caltech.edu/id/eprint/11824Stability of Spherically Symmetric, Charged Black Holes and Multipole Moments for Stationary Systems
https://resolver.caltech.edu/CaltechETD:etd-03132009-081222
Authors: {'items': [{'id': 'Gürsel-Halis-Yekta', 'name': {'family': 'Gürsel', 'given': 'Halis Yekta'}, 'show_email': 'NO'}]}
Year: 1983
DOI: 10.7907/e9t6-dr05
<p>This dissertation is written in two parts. Part I deals with the question of stability of a spherically symmetric, charged black hole against scalar, electromagnetic, and gravitational perturbations. It consists of two papers written in collaboration with Igor D. NoVikov, Vernon D. Sandberg and A. A. Starobinsky. In these papers we describe the dynamical evolution of these perturbations on the interior of a Reissner-Nordstrom black hole. The instability of the hole's Cauchy horizon is discussed in detail in terms of the energy densities of the test fields as measured by a freely falling observer approaching the Cauchy horizon. We conclude that the Cauchy horizon of the analytically extended Reissner-Nordstrom solution is highly unstable and not a physical feature of a realistic gravitational collapse. Part II of this dissertation addresses two problems closely connected with muitipole structure of stationary, asymptotically flat spacetimes. It consists of two papers written in collaboration with Kip S. Thorne despite the fact that his name does not appear on one of them. The first one (Paper III in this thesis) shows the equivalence of the moments defined by Kip S. Thorne and the moments defined by Robert Geroch and Richard Hansen. The second (Paper IV in this thesis) proves a conjecture by Kip S. Thorne: In the limit of "slow" motion, general relativistic gravity produces no changes whatsoever in the classical Euler equations of rigid body motion. We prove this conjecture by giving an algorithm for generating rigidly rotating solutions of Einstein's equations from nonrotating, static solutions.</p>
https://thesis.library.caltech.edu/id/eprint/945Topics in Supersymmetry Theory: 1. A Superspace Action for Ten-Dimensional Supersymmetric Yang-Mills Theory in Terms of Four-Dimensional Superfields; 2. Gauge Groups for Type-I Superstrings
https://resolver.caltech.edu/CaltechTHESIS:10232019-170411829
Authors: {'items': [{'id': 'Sagnotti-Augusto', 'name': {'family': 'Sagnotti', 'given': 'Augusto'}, 'show_email': 'NO'}]}
Year: 1983
DOI: 10.7907/qrfw-nf31
This thesis is an account or most of the work that I did in Supersymmetry and Supergravity over the last two years. It deals with two major topics. the construction of a new superspace action for ten-dimensional supersymmetric Yang-Mills theory in terms of four-dimensional superfields. and the classification of the gauge groups allowed at the classical level in the type-I superstring theory. In addition, it contains a discussion of work that I did showing the uniqueness of supergravity in eleven dimensions and the uniqueness of the free Rarita-Schwinger action for massless and massive spin-³/₂ fields.https://thesis.library.caltech.edu/id/eprint/11853Realistic Calculations of Excitations in Nuclear Matter
https://resolver.caltech.edu/CaltechTHESIS:10182019-162452942
Authors: {'items': [{'id': 'Kwong-Nai-Hang', 'name': {'family': 'Kwong', 'given': 'Nai-Hang'}, 'show_email': 'NO'}]}
Year: 1983
DOI: 10.7907/wcb1-mh63
<p>A numerical method has been developed to solve the RPA equation, exchange term included, in nuclear matter. The dynamic form factor S(q, ω) is extracted for several v4 and v6 phenomenological potentials, including the d1-potential of Gogny et al. The limits of validity of the long-wavelength (Landau) approximation and the often adopted local-kernel approximation are discussed. Substantial disagreements with the exact results are found for the latter. The method is then applied to solve a Jastrow-correlated extension of the RPA equation, using the hardcore OMY potential. Results of calculations performed in two-body cluster approximation and Fermi-Hypernetted-Chain (FHNC) approximation are compared. The two-body results predict an instability against density fluctuations, which disappears at the FHNC level. The validity and consequences of employing the FHNC effective potential within the self-consistent HF/RPA framework are discussed. Future developments include applying the method to other Fermi systems such as liquid <sup>3</sup>He and the microscopic calculation of Landau parameters.</p>https://thesis.library.caltech.edu/id/eprint/11828Topics in Black-Hole Physics: Geometric Constraints on Noncollapsing, Gravitating Systems and Tidal Distortions of a Schwarzschild Black Hole
https://resolver.caltech.edu/CaltechTHESIS:08232017-105535039
Authors: {'items': [{'id': 'Redmount-Ian-H', 'name': {'family': 'Redmount', 'given': 'Ian H.'}, 'show_email': 'NO'}]}
Year: 1984
DOI: 10.7907/mp3n-4r06
<p>This dissertation consists of two studies on the general-relativistic theory of black holes. The first work concerns the fundamental issue of black-hole formation: in it I seek geometric constraints on gravitating matter systems, in the special case of axial symmetry, which determine whether or not those systems undergo gravitational collapse to form black holes. The second project deals with mechanical behavior of a black hole: specifically, I study the tidal deformation of a static black hole by the gravitational fields of external bodies.</p>
<p>In the first paper I approach the problem of geometric constraints determining gravitational collapse or non-collapse through the initial-value formalism of general relativity. I construct initial-value data representing noncollapsing, nonsingular, axisymmetric matter systems and examine the constraints imposed on this construction by the initial-value equation derived from the Einstein field equations. The construction consists of a nonsingular, momentarily static interior geometry with nonnegative mass-energy density, matched smoothly to a static, vacuum exterior geometry (described by a Weyl solution of the Einstein field equations) at a boundary surface. The initial-value equation is found to impose restrictions on the choice of the boundary surface for such a system. Two such constraints are obtained here, appropriate to spherical and toroidal interior-region topologies. These constraints are studied by applying them to simple examples of Weyl exterior geometries. The "hoop conjecture" for the general geometric-constraints problem states that a system must collapse to a black hole unless its circumference in some direction exceeds a lower bound of the order of the system's mass. The examples examined here show, however, that the constraints derived in this study are not generally correlated with any simple measure of system size, and thus that they do not embody the hoop conjecture.</p>
<p>The second paper examines the tidal distortion of a Schwarzschild black hole by bodies ("moons") suspended above the horizon on "ropes." A solution of the Einstein field equations is constructed describing this configuration, using the Weyl formalism for axisymmetric, static, vacuum geometries. The intrinsic geometry of the tidally deformed black-hole horizon is obtained from this solution; I construct embedding diagrams to represent the shape of the horizon and the tidal bulges raised on it for both weak and strong perturbations. The relations among the masses of the hole and moons, the binding energy of the system, and the rope density and tension are calculated from the solution and shown to be mutually consistent. Also, the Riemann curvature tensor representing the tidal fields near the horizon is calculated. This solution is found to agree with a previous calculation by Hartle of black-hole tides, in the limit of perturbing moons far from the horizon. In the opposite case of moons very near the horizon, this solution approaches the static limit of the distorted horizon in Rindler space calculated by Suen and Price. The results of this study thus support the use of the Rindler approximation to Schwarzschild spacetime in calculating static black-hole tides, and its extension to dynamical situations.</p>https://thesis.library.caltech.edu/id/eprint/10385Finiteness in Supersymmetric Theories
https://resolver.caltech.edu/CaltechTHESIS:11262018-165108335
Authors: {'items': [{'id': 'Marcus-Neil', 'name': {'family': 'Marcus', 'given': 'Neil'}, 'show_email': 'NO'}]}
Year: 1984
DOI: 10.7907/4t2f-t947
<p>A two loop calculation in the N = 4 supersymmetric Yang Mills theory is performed in various dimensions. The theory is found to be two-loop finite in six dimensions or less, but infinite in seven and nine dimensions. The six-dimensional result can be explained by a formulation of the theory in terms of N = 2 superfields. The divergence in seven dimensions is naively compatible with both N=2 and N=4 superfield power counting rules, but is of a form that cannot be written as an on-shell N=4 superfield integral. The hypothesized N=4 extended superfield formalism therefore either does not exist, or at least has weaker consequences than would have been expected. By analogy, four-dimensional supergravity theories are expected to be infinite at three loops.</p>
<p>Some general issues about the meaning of finiteness in nonrenormalizable theories are discussed. In particular, the use of field redefinitions, the generalization of wavefunction renormalizations to nonrenormalizable theories, and whether counterterms should be used in calculations in "finite" theories are studied. It is shown that theories finite to n loops can have at most simple-pole divergences at n + 1 loops.</p>
<p>A method for simplifying the calculation of infinite parts of Feynman diagrams is developed. Based on the observation that counterterms are local functions, all integrals are reduced to logarithmically divergent ones with no dependence on masses or external momenta. The method is of general use, and is particularly effective for many-point Green functions at more than one loop.</p>https://thesis.library.caltech.edu/id/eprint/11284Yang-Mills Theory in Six-Dimensional Superspace
https://resolver.caltech.edu/CaltechTHESIS:06042014-113206988
Authors: {'items': [{'email': 'jkoller@alumni.caltech.edu', 'id': 'Koller-Jeffrey-George', 'name': {'family': 'Koller', 'given': 'Jeffrey George'}, 'show_email': 'YES'}]}
Year: 1984
DOI: 10.7907/RP3T-S865
<p>The superspace approach provides a manifestly supersymmetric formulation of supersymmetric theories. For N= 1 supersymmetry one can use either constrained or unconstrained superfields for such a formulation. Only the unconstrained formulation is suitable for quantum calculations. Until now, all interacting N>1 theories have been written using constrained superfields. No solutions of the nonlinear constraint equations were known.</p>
<p>In this work, we first review the superspace approach and its relation to conventional component methods. The difference between constrained and unconstrained formulations is explained, and the origin of the nonlinear constraints in supersymmetric gauge theories is discussed. It is then shown that these nonlinear constraint equations can be solved by transforming them into linear equations. The method is shown to work for N=1 Yang-Mills theory in four dimensions. </p>
<p>N=2 Yang-Mills theory is formulated in constrained form in six-dimensional superspace, which can be dimensionally reduced to four-dimensional N=2 extended superspace. We construct a superfield calculus for six-dimensional superspace, and show that known matter multiplets can be described very simply. Our method for solving constraints is then applied to the constrained N=2 Yang-Mills theory, and we obtain an explicit solution in terms of an unconstrained superfield. The solution of the constraints can easily be expanded in powers of the unconstrained superfield, and a similar expansion of the action is also given. A background-field expansion is provided for any gauge theory in which the constraints can be solved by our methods. Some implications of this for superspace gauge theories are briefly discussed. </p>
https://thesis.library.caltech.edu/id/eprint/8477Supergravity Theory from Ten Dimensions
https://resolver.caltech.edu/CaltechTHESIS:01312019-162531115
Authors: {'items': [{'id': 'Romans-Larry-James', 'name': {'family': 'Romans', 'given': 'Larry James'}, 'show_email': 'NO'}]}
Year: 1985
DOI: 10.7907/wt9n-gm39
<p>This work is concerned with the study of several ten-dimensional field theories intimately associated with superstring theories, and possibilities for obtaining realistic four-dimensional theories from them.</p>
<p>Three chapters follow the N = 2b supergravity from ten to five, then to four dimensions . First of all, compactifications to five dimensions on various manifolds are studied. Then the entire mass spectrum for the compactification on S<sup>5</sup> is derived using techniques of harmonic analysis on spheres. A particular set of modes corresponds to a gauged maximal super gravity theory in five dimensions; this theory, with Yang-Mills group SO(6), is constructed in detail. By a process similar to analytic continuation, noncompact versions of this theory are also obtained, gauging all the semisimple real forms of SO(6). One particular form, with gauge group SO*(6) ≈ SU(3,1), compactifies to fiat four-dimensional spacetime and offers attractive phenomenological possibilities.</p>
<p>The final chapter is concerned with candidates for effective low-energy theories for N = 1 superstrings with gauge group SO(32) or E<sub>8</sub> x E<sub>8</sub>. These effective theories contain curvature squared terms, and require unusual gravitational interactions to cancel anomalies. The field equations are derived and found to admit compactifications to fiat four dimensional spacetime, with the possibility of accommodating many phenomenological considerations.</p>https://thesis.library.caltech.edu/id/eprint/11373Auxiliary Field Monte-Carlo for Quantum Many-Body Systems
https://resolver.caltech.edu/CaltechTHESIS:01072019-110818820
Authors: {'items': [{'id': 'Sugiyama-Gayle-A', 'name': {'family': 'Sugiyama', 'given': 'Gayle A.'}, 'show_email': 'NO'}]}
Year: 1985
DOI: 10.7907/t9kp-qe57
<p>An algorithm is developed for determining the exact ground state properties of quantum many-body systems which is equally applicable to bosons and fermions. The Schroedinger eigenvalue equation for the ground state energy is recast into the form of a many-dimensional integral through the use of the Hubbard-Stratonovitch representation of the imaginary time many- body evolution operator. The resulting functional integral is then evaluated stochastically. The algorithm is tested for an exactly soluble boson system and is then extended to include fermions and repulsive potentials. Importance sampling is crucial to the success of the method, particularly for more complex systems. Improved computational efficiency is attained by performing the calculations in momentum space.</p>https://thesis.library.caltech.edu/id/eprint/11335The Abundances of Ultraheavy Elements in the Cosmic Radiation
https://resolver.caltech.edu/CaltechTHESIS:10092014-143512211
Authors: {'items': [{'id': 'Newport-Brian-John', 'name': {'family': 'Newport', 'given': 'Brian John'}, 'show_email': 'NO'}]}
Year: 1986
DOI: 10.7907/2bfw-r090
<p>Analysis of the data from the Heavy Nuclei Experiment on the HEAO-3 spacecraft has yielded the cosmic ray abundances of odd-even element pairs with atomic number, Z, in the range 33 ≤ Z ≤ 60, and the abundances of broad element groups in the range 62 ≤ Z ≤ 83, relative to iron. These data show that the cosmic ray source composition in this charge range is quite similar to that of the solar system provided an allowance is made for a source fractionation based on first ionization potential. The observations are inconsistent with a source composition which is dominated by either r-process or s-process material, whether or not an allowance is made for first ionization potential. Although the observations do not exclude a source containing the same mixture of r- and s-process material as in the solar system. the data are best fit by a source having an r- to s-process ratio of 1.22<sup>+0.25</sup><sub>-0.21</sub>, relative to the solar system The abundances of secondary elements are consistent with the leaky box model of galactic propagation, implying a pathlength distribution similar to that which explains the abundances of nuclei with Z < 29.</p>
<p>The energy spectra of the even elements in the range 38 ≤ Z ≤ 60 are found to have a deficiency of particles in the range ~1.5 to 3 GeV/amu, compared to iron. This deficiency may result from ionization energy loss in the interstellar medium, and is not predicted by propagation models which ignore such losses. ln addition, the energy spectra of secondary elements are found to be different to those of the primary elements. Such effects are consistent with observations of lighter nuclei, and are in qualitative agreement with galactic propagation models using a rigidity dependent escape length. The energy spectra of secondaries arising from the platinum group are found to be much steeper than those of lower Z. This effect may result from energy dependent fragmentation cross sections.</p>
https://thesis.library.caltech.edu/id/eprint/8688Interactions of Strings Compactified on Orbifolds
https://resolver.caltech.edu/CaltechTHESIS:08012017-135315454
Authors: {'items': [{'id': 'Hamidi-Shahram', 'name': {'family': 'Hamidi', 'given': 'Shahram'}, 'show_email': 'NO'}]}
Year: 1987
DOI: 10.7907/gvyt-8e89
<p>It is very important to understand the process of string compactification before one can extract any reliable phenomenology. We consider an exactly solvable method of string compactification, in which the internal space is an orbifold. We compute various interaction amplitudes and describe how other amplitudes can be calculated.</p>
<p>Multi-valued string variables are handled by formulating the amplitudes on covering spaces where they become single-valued. In the computation of the amplitudes, stretched string intermediate states give rise to expressions that are non-perturbative from the non-linear sigma model point of view.</p>
<p>We also discuss, in the context of Z orbifold, the "blowing up" of the fixed points of an orbifold, to give rise to a Calabi-Yau manifold. The resulting Calabi-Yau manifold is shown to be non-perturbatively stable.</p>https://thesis.library.caltech.edu/id/eprint/10358The Singular Mechanics of Particles and Strings
https://resolver.caltech.edu/CaltechTHESIS:01172013-111439406
Authors: {'items': [{'id': 'Allen-Theodore-John', 'name': {'family': 'Allen', 'given': 'Theodore John'}, 'show_email': 'NO'}]}
Year: 1988
DOI: 10.7907/hvjy-be63
<p>The quantum mechanics of singular systems is a topic of considerable importance for all the theories of elementary particle physics in which gauge invariance is a universal attribute. This is especially true for string theories which are gauge theories <i>par excellence</i>.</p>
<p>This thesis begins with a brief exposition of singular Hamiltonian mechanics. This tool is applied principally to manifestly supersymmetric particle and string theories. The Dirac particle and the bosonic particle and string are briefly examined. In particular, a method is shown for quantizing the point superparticle in four and ten dimensions. The two actions proposed for describing the manifestly supersymmetric string are shown to be essentially equivalent. The problems of their quantization are briefly discussed.</p>https://thesis.library.caltech.edu/id/eprint/7402A Measurement of the Proton Elastic Form Factors for 1 ≤ Q² ≤ 3 (GeV/c)²
https://resolver.caltech.edu/CaltechTHESIS:10242013-084941401
Authors: {'items': [{'id': 'Walker-Robert-Christian-David', 'name': {'family': 'Walker', 'given': 'Robert Christian David'}, 'show_email': 'NO'}]}
Year: 1989
DOI: 10.7907/1j3p-xf48
<p>We report measurements of the proton form factors, Gᵖ<sub>E</sub> and Gᵖ<sub>M</sub>, extracted from elastic electron scattering in the range 1 ≤ Q² ≤ 3 (GeV/c)² with uncertainties of < 15% in Gᵖ<sub>E</sub> and < 3% in Gᵖ<sub>M</sub>. The results for Gᵖ<sub>E</sub> are somewhat larger than indicated by most theoretical parameterizations. The ratio of Pauli and Dirac form factors, Q²(Fᵖ₂/Fᵖ₁), is lower in value and demonstrates less Q² dependence than these parameterizations have indicated. Comparisons are made to theoretical models, including those based on perturbative QCD, vector-meson dominance, QCD sum rules, and diquark constituents to the proton. A global extraction of the form factors, including previous elastic scattering measurements, is also presented.</p>https://thesis.library.caltech.edu/id/eprint/8007Diffraction-Limited Imaging on the 200-Inch Telescope
https://resolver.caltech.edu/CaltechTHESIS:06032013-115455313
Authors: {'items': [{'id': 'Nakajima-Tadashi', 'name': {'family': 'Nakajima', 'given': 'Tadashi'}, 'show_email': 'NO'}]}
Year: 1989
DOI: 10.7907/hgnx-x451
<p>We have used the technique of non-redundant masking at the Palomar 200-inch telescope and radio VLBI imaging software to make optical aperture synthesis maps of two binary stars, β Corona Borealis and σ Herculis. The dynamic range of the map of β CrB, a binary star with a separation of 230 milliarcseconds is 50:1. For σ Her, we find a separation of 70 milliarcseconds and the dynamic range of our image is 30:1. These demonstrate the potential of the non-redundant masking technique for diffraction-limited imaging of astronomical objects with high dynamic range.</p>
<p>We find that the optimal integration time for measuring the closure phase is longer than that for measuring the fringe amplitude. There is not a close relationship between amplitude errors and phase errors, as is found in radio interferometry. Amplitude self calibration is less effective at optical wavelengths than at radio wavelengths. Primary beam sensitivity correction made in radio aperture synthesis is not necessary in optical aperture synthesis.</p>
<p>The effects of atmospheric disturbances on optical aperture synthesis have been studied by Monte Carlo simulations based on the Kolmogorov theory of refractive-index fluctuations. For the non-redundant masking with τ<sub>c</sub>-sized apertures, the simulated fringe amplitude gives an upper bound of the observed fringe amplitude. A smooth transition is seen from the non-redundant masking regime to the speckle regime with increasing aperture size. The fractional reduction of the fringe amplitude according to the bandwidth is nearly independent of the aperture size. The limiting magnitude of optical aperture synthesis with τ<sub>c</sub>-sized apertures and that with apertures larger than τ<sub>c</sub> are derived.</p>
<p>Monte Carlo simulations are also made to study the sensitivity and resolution of the bispectral analysis of speckle interferometry. We present the bispectral modulation transfer function and its signal-to-noise ratio at high light levels. The results confirm the validity of the heuristic interferometric view of image-forming process in the mid-spatial-frequency range. The signal-to-noise ratio of the bispectrum at arbitrary light levels is derived in the mid-spatial-frequency range.</p>
<p>The non-redundant masking technique is suitable for imaging bright objects with high resolution and high dynamic range, while the faintest limit will be better pursued by speckle imaging.</p>https://thesis.library.caltech.edu/id/eprint/7823Voltage-Sensitive Dye Recording from Networks of Cultured Neurons
https://resolver.caltech.edu/CaltechETD:etd-06082007-080125
Authors: {'items': [{'id': 'Chien-Chi-Bin', 'name': {'family': 'Chien', 'given': 'Chi-Bin'}, 'show_email': 'NO'}]}
Year: 1990
DOI: 10.7907/jwsd-2f67
<p>This thesis describes the development and testing of a sensitive apparatus for recording electrical activity from microcultures of rat superior cervical ganglion (SCG) neurons by using voltage-sensitive fluorescent dyes.</p>
<p>The apparatus comprises a feedback-regulated mercury arc light source, an inverted epifluorescence microscope, a novel fiber-optic camera with discrete photodiode detectors, and low-noise preamplifiers. Using an NA 0.75 objective and illuminating at 10 W/cm² with the 546 nm mercury line, a typical SCG neuron stained with the styryl dye RH423 gives a detected photocurrent of 1 nA; the light source and optical detectors are quiet enough that the shot noise in this photocurrent--about.03% rms--dominates. The design, theory, and performance of this dye-recording apparatus are discussed in detail.</p>
<p>Styryl dyes such as RH423 typically give signals of 1%/100 mV on these cells; the signals are linear in membrane potential, but do not appear to arise from a purely electrochromic mechanism. Given this voltage sensitivity and the noise level of the apparatus, it should be possible to detect both action potentials and subthreshold synaptic potentials from SCG cell bodies. In practice, dye recording can easily detect action potentials from every neuron in an SCG microculture, but small synaptic potentials are obscured by dye signals from the dense network of axons.</p>
<p>In another microculture system that does not have such long and complex axons, this dye-recording apparatus should be able to detect synaptic potentials, making it possible to noninvasively map the synaptic connections in a microculture, and thus to study long-term synaptic plasticity.</p>https://thesis.library.caltech.edu/id/eprint/2517Non-Conservation of Baryon Number at High Energy in the Standard Model
https://resolver.caltech.edu/CaltechETD:etd-06062007-160632
Authors: {'items': [{'id': 'Espinosa-Olivier-R', 'name': {'family': 'Espinosa', 'given': 'Olivier R.'}, 'show_email': 'NO'}]}
Year: 1990
DOI: 10.7907/74cf-xv77
<p>We calculate the coupling constant and energy dependence of the scattering amplitudes for baryon- and lepton-number violating processes in the context of the standard model, in the semiclassical approximation. It is found that, to leading order in this expansion, the spin-averaged total cross sections for these processes grow as a power of the CM-energy and thus violate the bound imposed by unitarity. This result has a twofold implication: first, perturbation theory in the instanton sector of the electroweak theory must break down at high energies and, second, it strongly suggests that baryon and lepton number non-conservation might be observed experimentally at energies accesible in the near future.</p>https://thesis.library.caltech.edu/id/eprint/2482Listening to the Ear
https://resolver.caltech.edu/CaltechTHESIS:09072011-150449036
Authors: {'items': [{'id': 'Shera-Christopher-A', 'name': {'family': 'Shera', 'given': 'Christopher A.'}, 'show_email': 'NO'}]}
Year: 1992
DOI: 10.7907/VAK9-MK96
Otoacoustic emissions demonstrate that the ear creates sound while listening to sound, offering a promising acoustic window on the mechanics of hearing in awake, listening human beings. That window is clouded, however, by an incomplete knowledge of wave reflection and transmission, both forth and back within the cochlea and through the middle ear. This thesis "does windows,"
addressing wave propagation and scattering on both sides of the middle ear. A summary of highlights follows.
Measurements of the cochlear input impedance in cat are used to identify a new symmetry in cochlear mechanics-termed
"tapering symmetry" after its geometric interpretation in simple models-that guarantees that the wavelength of the traveling wave changes slowly with position near the stapes.
Waves therefore propagate without reflection through the basal turns of the cochlea. Analytic methods for solving the cochlear wave equations using a perturbative scattering
series are given and used to demonstrate that, contrary to common belief, conventional cochlear models exhibit
negligible internal reflection whether or not they accurately represent the tapering symmetries of the inner ear. Frameworks for the systematic "deconstruction" of eardrum and middle-ear transduction characteristics are developed and applied to the analysis of noninvasive measurements of middle-ear and cochlear mechanics. A simple
phenomenological model of inner-ear compressibility that correctly predicts hearing thresholds in patients with missing or disarticulated middle-ear ossicles is developed and used to establish an upper bound on cochlear
compressibility several orders of magnitude smaller than that provided by direct measurements. Accurate measurements of stimulus frequency evoked otoacoustic emissions are performed and used to determine the form and frequency variation of the cochlear traveling-wave ratio
noninvasively. Those measurements are inverted to obtain the spatial distribution of mechanical inhomogeneities
responsible for evoked emission. Although current models require that the periodicities found in emission spectra and threshold hearing curves originate in a corresponding corrugation in the mechanics of the cochlea, it is shown that the observed spectral periodicities can arise spontaneously through the dynamics of wave propagation and reflection and that the organ of Corti, as suggested by the anatomy, need manifest no particular translational
symmetries.https://thesis.library.caltech.edu/id/eprint/6653The infinite range Heisenberg model and high temperature superconductivity
https://resolver.caltech.edu/CaltechETD:etd-05042006-112846
Authors: {'items': [{'email': 'jamil@wag.caltech.edu', 'id': 'Tahir-Kheli-J', 'name': {'family': 'Tahir-Kheli', 'given': 'Jamil'}, 'show_email': 'YES'}]}
Year: 1992
DOI: 10.7907/9JDD-4P11
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
The thesis deals with the theory of high temperature superconductivity from the standpoint of three-band Hubbard models.
Chapter 1 of the thesis proposes a strongly coupled variational wavefunction that has the three-spin system of an oxygen hole and its two neighboring copper spins in a doublet and the background Cu spins in an eigenstate of the infinite range antiferromagnet. This wavefunction is expected to be a good "zeroth order" wavefunction in the superconducting regime of dopings. The three-spin polaron is stabilized by the hopping terms rather than the copper-oxygen antiferromagnetic coupling Jpd. Considering the effect of the copper-copper antiferromagnetic coupling Jdd, we show that the three-spin polaron cannot be pure Emery (Dg), but must have a non-negligible amount of doublet-u (Du) character for hopping stabilization. Finally, an estimate is made for the magnitude of the attractive coupling of oxygen holes.
Chapter 2 presents an exact solution to a strongly coupled Hamiltonian for the motion of oxygen holes in a 1-D Cu-O lattice. The Hamiltonian separates into two pieces: one for the spin degrees of freedom of the copper and oxygen holes, and the other for the charge degrees of freedom of the oxygen holes. The spinon part becomes the Heisenberg antiferromagnet in 1-D that is soluble by the Bethe Ansatz. The holon piece is also soluble by a Bethe Ansatz with simple algebraic relations for the phase shifts.
Finally, we show that the nearest neighbor Cu-Cu spin correlation increases linearly with doping and becomes positive at x [...] 0.70.https://thesis.library.caltech.edu/id/eprint/1605The Multiplicity of T Tauri Stars in the Star Forming Regions Taurus-Auriga and Ophiucus-Scorpius: A 2.2 µm Speckle Imaging Survey
https://resolver.caltech.edu/CaltechETD:etd-10072004-143305
Authors: {'items': [{'email': 'ghez@astro.ucla.edu', 'id': 'Ghez-Andrea-Mia', 'name': {'family': 'Ghez', 'given': 'Andrea Mia'}, 'orcid': '0000-0003-3230-5055', 'show_email': 'YES'}]}
Year: 1993
DOI: 10.7907/AD5X-DA38
<p>We present the results of a magnitude limited (K ≤ 8.5 mag) multiplicity survey of T Tauri stars (TTS) in two nearby star forming regions (SFR), Taurus-Auriga and Ophiuchus-Scorpius. Each of the 69 stars in the sample was observed at K(2.2 µm) with an infrared array camera on the Hale 5-m Telescope at Palomar Observatory and imaged using two-dimensional speckle interferometric techniques.</p>
<p>Thirty three companion stars were found, of which 15 were new detections. A subset of 64 observations was sensitive to all companion stars in the projected linear range 14 to 225 AU and the magnitude difference range 0.0 to 2.0 mag. We used this subset and region to study the multiplicity of TTS; the frequency of companion stars within this region is 34 ± 9%, independent of SFR. We discovered a distinction between the classical TTS (CTTS) and the weak-lined TTS (WTTS) based on the binary star frequency as a function of separation; <i>the WITS dominate the binary star distribution at the closer separations and the CTTS populate the wider separations</i>. The cross over occurred near 100 AU, the size typically quoted for a circumstellar disk. We suggest that all TTS begin as CTTS and become WTTS when accretion has ceased, and that the nearby companion stars act to shorten the accretion timescale in multiple star systems.</p>
<p>Integrated over all magnitude differences the binary star frequency in the projected linear separation range 14 to 225 AU for TTS (59 ± 16%) is a factor of 3.5 greater than that of the solar-type main sequence stars (17 ± 3%). Given the limited angular separation range that we are sensitive to, i.e., both the spectroscopic and wide binaries are missed, the rate at which binaries are detected suggests that <i>most, if not all, TTS stars have companions</i>. We propose that the observed overabundance of companions to TTS with respect to their older counterparts on the main sequence is an evolutionary effect; in this scheme triple and higher order TTS, which are observed at higher frequencies than for the solar-type main sequence stars, are disrupted by close encounters with another star or system of stars.</p>https://thesis.library.caltech.edu/id/eprint/3971Asymptotic scaling in the two-dimensional O(3) Nonlinear sigma model: a Monte Carlo study on parallel computers
https://resolver.caltech.edu/CaltechTHESIS:05012013-113552586
Authors: {'items': [{'id': 'Apostolakis-J', 'name': {'family': 'Apostolakis', 'given': 'John'}, 'show_email': 'NO'}]}
Year: 1994
DOI: 10.7907/be1d-0t13
<p>We investigate the 2d O(3) model with the standard action by Monte Carlo simulation at couplings β up to 2.05. We measure the energy density, mass gap and susceptibility of the model, and gather high statistics on lattices of size L ≤ 1024 using the Floating Point Systems T-series vector hypercube and the Thinking Machines Corp.'s Connection Machine 2. Asymptotic scaling does not appear to set in for this action, even at β = 2.10, where the correlation length is 420. We observe a 20% difference between our estimate m/Λ^─_(Ms) = 3.52(6) at this β and the recent exact analytical result . We use the overrelaxation algorithm interleaved with Metropolis updates and show that decorrelation time scales with the correlation length and the number of overrelaxation steps per sweep. We determine its effective dynamical critical exponent to be z' = 1.079(10); thus critical slowing down is reduced
significantly for this local algorithm that is vectorizable and parallelizable.</p>
<p>We also use the cluster Monte Carlo algorithms, which are non-local Monte Carlo update schemes which can greatly increase the efficiency of computer simulations of spin models. The major computational task in these algorithms is connected component labeling, to identify clusters of connected sites on a lattice. We have devised some new SIMD component labeling algorithms, and implemented them on the Connection Machine. We investigate their performance when applied to the cluster update of the two dimensional
Ising spin model.</p>
<p>Finally we use a Monte Carlo Renormalization Group method to directly measure the couplings of block Hamiltonians at different blocking levels. For the usual averaging block transformation we confirm the renormalized trajectory (RT) observed by Okawa. For another improved probabilistic block transformation we find the RT, showing that it is much closer to the Standard Action. We then use this block transformation to obtain the discrete β-function of the model which we compare to the perturbative result. We do not see convergence, except when using a rescaled coupling β_E to effectively resum the series. For the latter case we see agreement for m/ Λ^─_(Ms) at , β = 2.14, 2.26, 2.38 and 2.50. To three loops m/Λ^─_(Ms) = 3.047(35) at β = 2.50, which is very close to the exact value m/ Λ^─_(Ms) = 2.943. Our last point at β = 2.62 disagrees with this estimate however.</p>
https://thesis.library.caltech.edu/id/eprint/7649Heavy hadrons in the large Nc limit
https://resolver.caltech.edu/CaltechETD:etd-09172007-144702
Authors: {'items': [{'id': 'Chow-C', 'name': {'family': 'Chow', 'given': 'Chi-Keung'}, 'show_email': 'NO'}]}
Year: 1995
DOI: 10.7907/7qz6-sg17
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
In the heavy quark and large [...] limit, heavy baryons can be identified as bound states of heavy mesons and light baryons. The binding potential can be calculated under chiral perturbation theory, and is simple harmonic when [...]. The spectra and properties of these bound states agree reasonably well with the observed heavy baryons. In this framework, some non-perturbative quantities, like the orbital excitation energy and the slope of the Isgur-Wise form factor, can be evaluated. Moreover, the same universal Isgur-Wise form factor describes the semileptonic decays [...] and [...]. The formalism can also be used to study the spectra, stabilities and decay modes of exotic multiquark states.https://thesis.library.caltech.edu/id/eprint/3584The Hierarchical Algorithms - Theory and Applications
https://resolver.caltech.edu/CaltechETD:etd-10252007-091003
Authors: {'items': [{'id': 'Su-Zheng-Yao', 'name': {'family': 'Su', 'given': 'Zheng-Yao'}, 'show_email': 'NO'}]}
Year: 1995
DOI: 10.7907/3nfb-m047
<p>Monte Carlo simulations are one of the most important numerical techniques for investigating statistical physical systems. Among these systems, spin models are a typical example which also play an essential role in constructing the abstract mechanism for various complex systems. Unfortunately, traditional Monte Carlo algorithms are afflicted with "critical slowing down" near continuous phase transitions and the efficiency of the Monte Carlo simulation goes to zero as the size of the lattice is increased. To combat critical slowing down, a very different type of collective-mode algorithm, in contrast to the traditional single-spin-flipmode, was proposed by Swendsen and Wang in 1987 for Potts spin models. Since then, there has been an explosion of work attempting to understand, improve, or generalize it. In these so-called "cluster" algorithms, clusters of spin are regarded as one template and are updated at each step of the Monte Carlo procedure. In implementing these algorithms the cluster labeling is a major time-consuming bottleneck and is also isomorphic to the problem of computing connected components of an undirected graph seen in other application areas, such as pattern recognition.</p>
<p>A number of cluster labeling algorithms for sequential computers have long existed. However, the dynamic irregular nature of clusters complicates the task of finding good parallel algorithms and this is particularly true on SIMD (single-instruction-multiple-data machines. Our design of the Hierarchical Cluster Labeling Algorithm aims at alleviating this problem by building a hierarchical structure on the problem domain and by incorporating local and nonlocal communication schemes. We present an estimate for the computational complexity of cluster labeling and prove the key features of this algorithm (such as lower computational complexity, data locality, and easy implementation) compared with the methods formerly known. In particular, this algorithm can be viewed as a generalized scan scheme applicable to problem domains of any high dimension and of arbitrary geometry (scan is an important primitive of parallel computing). In addition, from implementation results, the hierarchical cluster labeling algorithm has proved to work equally well on MIMD machines, though originally designed for SIMD machines.</p>
<p>Based on this success, we further study the hierarchical structure hidden in the algorithm. Hierarchical structure is a conceptual framework frequently used in building models for the study of a great variety of problems. This structure serves not only to describe the complexity of the system at different levels, but also to achieve some goals targeted by the problem, i.e., an algorithm to solve the problem. In this regard, we investigate the similarities and differences between this algorithm and others, including the FFT and the Barnes-Hut method, in terms of their hierarchical structures.</p>
https://thesis.library.caltech.edu/id/eprint/4257Electron energy loss spectroscopic study of small molecules on transition metal surfaces
https://resolver.caltech.edu/CaltechETD:etd-10122007-112248
Authors: {'items': [{'id': 'Wang-Youqi', 'name': {'family': 'Wang', 'given': 'Youqi'}, 'show_email': 'NO'}]}
Year: 1995
DOI: 10.7907/h31m-na55
The scheme of ultrahigh-resolution electron energy loss spectroscopy (UNREELS) is described in detail with graphical examples of the real data processing. On the basis of modern digital information processing techniques, this method promises to yield EEL spectra with the ultimate resolution and superior signal to noise ratio.
The interaction of ammonia with clean and chemically modified Ru(001) surfaces were studied by using HREELS, TPD, and LEED techniques under UHV condition. Ammonia is found to interact with the surface chiefly through its lone-pair electrons, evidenced by the blue-shift of ammonia symmetric deformation mode and the increase of thermal desorption temperature of ammonia on both oxygen and nitrogen modified surfaces. No detectable dissociation of ammonia is found under the specified conditions.
The reactions of gas-phase atomic hydrogen with oxygen and carbon monoxide pre-adsorbed on Ru(001) surface at low temperature were studied via HREELS technique. The experimental results can be understood via an Eley-Rideal-like mechanism.
The decomposition mechanism of methylamine on Ru(001) surface was investigated by HREELS and TPD techniques. The cyanide adspecies was found to be side-on bonded on the ruthenium surface and its bond order is reduced from three to two.
https://thesis.library.caltech.edu/id/eprint/4055A Study of Bhabha Scattering at the Z Resonance
https://resolver.caltech.edu/CaltechTHESIS:05172021-190748275
Authors: {'items': [{'email': 'wenwen.lu@jpl.nasa.gov', 'id': 'Lu-Wenwen', 'name': {'family': 'Lu', 'given': 'Wenwen'}, 'show_email': 'NO'}]}
Year: 1998
DOI: 10.7907/kyrx-3v72
<p>In this thesis, I present a study on Bhabha scattering at the Z resonance using
the 13 detector at 1EP. I have measured the cross section and forward-backward
asymmetry measurement for the process e⁺e⁻ → e⁺e⁻(nγ) in the large angle region
( 44° < θe⁺e⁻ < 136°). The data used was collected during 1993 (3 energy points
at the Z resonance) and 1994 (Peak point only), corresponding to a total of 66,000
e⁺e⁻ pairs. The results of my measurement are combined with those from other 13
measurements of Z production and decays to provide a precision test of the Standard
Model. Electroweak parameters are determined with unprecedented precision.</p>
<p>The main results in this thesis are as follows:
<ul>
<li>the cross section of e⁺e⁻ → e⁺e⁻(nγ) process at the Z peak: σ = 1.072 ± 0.005 (stat.) ± 0.002 (sys.) nb,</li>
<li>the forward-backward asymmetry of e⁺e⁻ → e⁺e⁻(nγ) process at the peak: A<sub>FB</sub> = 0.122 ± 0.006 (stat.) ± 0.003 (sys.),</li>
<li>the mass of the Z boson: Mz = 91188.3 ± 2.9 MeV,</li>
<li>the total width of the Z boson: Γz = 2499.8 ± 4.3 MeV,</li>
<li>the partial decay width of the Z boson into electrons: Γe = 83.99 ± 0.26 MeV,</li>
<li>the Z electroweak coupling constants to fermions: -ℓ/g<sub>V</sub>, -ℓ/g<sub>A</sub> = -0.5010 ± 0.0006,</li>
<li>the effective weak mixing angle: sin² θ̅ <sub>w</sub> = 0.2304 ± 0.0009,</li>
<li>the mass of the top quark: M<sub>t</sub> = 189<sup>+12</sup><sub>-13</sub> ± 17 GeV,</li>
<li>the mass of the Higgs boson: M<sub>H</sub> = 91<sup>+230</sup><sub>-81</sub> GeV; M<sub>H</sub> < 645 GeV 95% CL.</li>
</ul></p>
<p>All the results from different measurements yield consistent results. No indication
of a deviation from the Standard Model has been observed.</p>https://thesis.library.caltech.edu/id/eprint/14151Large Scale Molecular Simulations with Application to Polymers and Nano-Scale Materials
https://resolver.caltech.edu/CaltechTHESIS:10202009-133456579
Authors: {'items': [{'id': 'Gao-Guanghua', 'name': {'family': 'Gao', 'given': 'Guanghua'}, 'show_email': 'NO'}]}
Year: 1998
DOI: 10.7907/69rm-7y79
There remain practical problems to predicting structures and properties of materials from first principles, though the foundation, quantum mechanics, has been established for many years. The goals of this research are to develop methods and tools that are accurate and practical, and apply them to important problems. Two aspects of the methodology are focused.
1. The development of accurate force fields based on ab initio quantum mechanical calculations on prototype systems. Procedures were developed on polyvinyl chloride (PVC) and successfully applied on other types of polymers. They are very important to studying of amorphous polymers materials, for which current methods have not been useful in predicting important properties (e.g. moduli and glass temperature).
2. The development of Massive Parallel Simulation (MPSim) Software. MPSim is suitable for large systems (millions of atoms). It has the ability of including environmental variables (temperature, pressure, tension, and shear) and extracting physical properties (moduli and glass temperatures). The theories and algorithms implemented are summarized in the Appendix.
These methods and tools are applied to the accurate simulation of structures and properties of amorphous polymer materials and nano-materials.
Molecular dynamics (MD) simulation on polyethylene (chapter 6) was used to develop a general strategy for predicting glass transition temperatures which is expected to be very important in polymer industry. In chapter 7, these strategies were successfully applied to three important fluoro polymers.
Single-walled carbon nanotubes (SWNT), recently discovered but not very well characterized, is an interesting new class of materials. Using an accurate force field, structures and mechanical properties of these systems are studied. Chapter 2 shows that the dominating factor for deciding stable structures and mechanical properties is the tube size, not chirality. The behavior of (10, 10) nano-tube under bending are studied (chapter 3) based on energy of hypothetical toroids with different radii. Yielding curvature of 1/R_s (R_s = 183.3 (Å)) where elastic bending becomes plastic response is found. In chapter 4, closest packing of K_5C_(80) with the distribution of K atoms along tube surface similar to the stacking of stage one K_1C_8 is established as the optimum structure of K-doped SWNT crystal.
https://thesis.library.caltech.edu/id/eprint/5314Inclusive Electron Scattering from Nuclei at x > 1 and High Q²
https://resolver.caltech.edu/CaltechTHESIS:02252021-181557347
Authors: {'items': [{'id': 'Arrington-John-R', 'name': {'family': 'Arrington', 'given': 'John R.'}, 'show_email': 'NO'}]}
Year: 1998
DOI: 10.7907/wkge-my02
<p>CEBAF experiment e89-008 measured inclusive electron scattering from nuclei in a Q<sup>2</sup> range between 0.8 and 7.3 (GeV/c)<sup>2</sup> for x<sub>Bjorken</sub> ≳ 1. The cross sections for scattering from D, C, Fe, and Au were measured. The C, Fe, and Au data have been analyzed in terms of F(y) to examine y-scaling of the quasielastic scattering, and to study the momentum distribution of the nucleons in the nucleus. The data have also been analyzed in terms of the structure function νW<sub>2</sub> to examine scaling of the inelastic scattering in x and ξ, and to study the momentum distribution of the quarks. In the regions where quasielastic scattering dominates the cross section (low Q<sup>2</sup> or large negative values of y), the data are shown to exhibit y-scaling. However, the y-scaling breaks down once the inelastic contributions become large. The data do not exhibit x-scaling, except at the lowest values of x, while the structure function does appear to scale in the Nachtmann variable, ξ.</p>https://thesis.library.caltech.edu/id/eprint/14096Order of Magnitude Physics: A Textbook with Applications to the Retinal Rod and the Density of Prime Numbers
https://resolver.caltech.edu/CaltechTHESIS:10302009-110303489
Authors: {'items': [{'email': 'sanjoy@mit.edu', 'id': 'Mahajan-Sanjoy-Sondhi', 'name': {'family': 'Mahajan', 'given': 'Sanjoy Sondhi'}, 'show_email': 'YES'}]}
Year: 1998
DOI: 10.7907/8MJZ-A984
<p>I develop tools to amplify our mental senses: our intuition and reasoning abilities. The first five chapters—based on the Order of Magnitude Physics class taught at Caltech by Peter Goldreich and Sterl Phinney—form part of a textbook on dimensional analysis, approximation, and physical reasoning. The text is a resource of intuitions, problem-solving methods, and physical interpretations. By avoiding mathematical complexity, order-of-magnitude techniques increase our physical understanding, and allow us to study otherwise difficult or intractable problems. The textbook covers: (1) simple estimations, (2) dimensional analysis, (3) mechanical properties of materials, (4) thermal properties of materials, and (5) water waves.</p>
<p>As an extended example of order-of-magnitude methods, I construct an analytic model for the flash sensitivity of a retinal rod. This model extends the flash-response model of Lamb and Pugh with an approximate model for steady-state response as a function of background light I<sub>b</sub>. The combined model predicts that the flash sensitivity is proportional to I<sub>b</sub><sup>-1.3</sup>. This result roughly agrees with experimental data, which show that the flash sensitivity follows the Weber-Fechner behavior of I<sub>b</sub><sup>-1</sup> over an intensity range of 100. Because the model is simple, it shows clearly how each biochemical pathway determines the rod's response.</p>
<p>The second example is an approximate model of primality, the square-root model. Its goal is to explain features of the density of primes. In this model, which is related to the Hawkins' random sieve, divisibility and primality are probabilistic. The model implies a recurrence for the probability that a number n is prime. The asymptotic solution to the recurrence is (log n)<sup>-1</sup>, in agreement with the prime-number theorem. The next term in the solution oscillates around (log n)<sup>-1</sup> with a period that grows superexponentially. These oscillations are a model for oscillations in the density of actual primes first demonstrated by Littlewood, who showed that the number of primes ≤ n crosses its natural approximator, the logarithmic integral, infinitely often. No explicit crossing is known; the best theorem, due to to Riele, says that the first crossing happens below 7 x 10<sup>370</sup>. A consequence of the square-root model is the conjecture that the first crossing is near 10<sup>27</sup>.</p>
https://thesis.library.caltech.edu/id/eprint/5338Diffusion in Amorphous Media
https://resolver.caltech.edu/CaltechTHESIS:10232009-112246663
Authors: {'items': [{'id': 'Iotov-Mihail-S', 'name': {'family': 'Iotov', 'given': 'Mihail S.'}, 'show_email': 'NO'}]}
Year: 1998
DOI: 10.7907/9b0m-2j57
The goals of this research are twofold: First, to develop methods and tools for studying problems in chemistry, material science and biology, as well as accurate prediction of the properties of structures and materials of importance to those fields. Second, use those tools to apply the methods to practical problems. In terms of methodology development this thesis focuses on two topics: One: Development of a massively parallel computer program to perform electronic, atomic, molecular levels simulations of problems in chemistry, material science and biology. This computer program uses existing and emerging hardware platforms and parallel tools and is based on decades long research in computer modeling and algorithms. We report on that development in Chapter 3. Two: Development of tools for Molecular Dynamics simulation and methods and tools for course-grained meso-scale modeling of transport properties and especially diffusion of gas penetrants in polymers. We have formulated a new method for extracting coarse-grained information from short (0.2-0.5 nanoseconds [ns]) MD simulations and use this in a meso-scale simulation to calculate diffusion constants in polymer matrices. This is a grid-based method, which calculates the average probability of each grid point of being a void and performs constrained and biased Monte Carlo (MC) dynamics to reach much longer time regimes than possible in MD. The MC method mimics the three regimes of mean square deviation (MSD) behavior seen in MD, thus accounting for the proper mobility of the voids and the compressibility of the polymer matrix. Theoretical discussions and justification for the method is presented in chapter 6. Initial results on He diffusion in a low-density polyethylene (PE) matrix are presented in chapter 7. The behavior at different temperatures follows closely the trend observed from calibrating long term MD for this particular system.
https://thesis.library.caltech.edu/id/eprint/5325Analytical and Numerical Studies of Waveguiding and Coupling in Periodic Dielectric Materials
https://resolver.caltech.edu/CaltechETD:etd-01032005-131558
Authors: {'items': [{'email': 'yx.photonics@gmail.com', 'id': 'Xu-Yong-Physics', 'name': {'family': 'Xu', 'given': 'Yong'}, 'orcid': '0000-0001-5849-032X', 'show_email': 'YES'}]}
Year: 2001
DOI: 10.7907/9988-YR54
<p>Using both analytical approaches and finite difference time domain simulations, we investigate different types of waveguiding and coupling mechanisms, including direct coupling between the optical resonators, waveguide-resonator coupling, indirect resonator coupling via waveguide modes, and Bragg reflection in cylindrically symmetric geometries.</p>
<p>By coupling an array of high Q optical resonators together, we form a new type of waveguide, coupled resonator optical waveguide (CROW), where photons propagate by "hopping" from one resonator to its nearest neighbors. Using tight-binding approximation, we find that the CROW band dispersion can be simply characterized by a coupling coefficient κ. The tight-binding results are confirmed by using the finite difference time domain algorithms to analyze two examples of CROW’s: one is composed of coupled defect cavities in a two-dimensional triangular lattice photonic crystal, while the other is formed by coupling an array of dielectric microdisk cavities.</p>
<p>By coupling a resonator to a waveguide, we significantly change the reflection and transmission characteristics of the waveguide. The waveguide dispersion can also be drastically modified by coupling an array of resonators to the waveguide, due to indirect coupling between the resonators via waveguide modes. Using a formalism based on the quantum scattering theory, we investigate how the waveguide-resonator coupling, resonator gain (loss), degeneracy and symmetries of the resonator modes influence the optical properties of such coupled waveguide-resonator systems.</p>
<p>Bragg guiding can be achieved in cylindrically symmetric geometries by using cladding media with alternating high and low refractive indices. Examples include Bragg fibers and dielectric coaxial fibers. An asymptotic formalism is developed to study the dispersion, propagation loss, and field distribution of guided modes in such fibers. The results are compared with those obtained from numerical calculations, where excellent agreement is found between the two approaches.</p>https://thesis.library.caltech.edu/id/eprint/7SU(3) Chiral Symmetry in Non-Relativistic Field Theory
https://resolver.caltech.edu/CaltechETD:etd-08172001-054126
Authors: {'items': [{'id': 'Ouellette-Stephen-Michael', 'name': {'family': 'Ouellette', 'given': 'Stephen Michael'}, 'show_email': 'NO'}]}
Year: 2001
DOI: 10.7907/JN2B-5X12
Applications imposing SU(3) chiral symmetry on non-relativistic field theories are considered. The first example is a calculation of the self-energy shifts of the spin-3/2 decuplet baryons in nuclear matter, from the chiral effective Lagrangian coupling octet and decuplet baryon fields. Special attention is paid to the self-energy of the Delta baryon near the saturation density of nuclear matter. We find contributions to the mass shifts from contact terms in the effective Lagrangian with coefficients of unknown value. As a second application, we formulate an effective field theory with manifest SU(2) chiral symmetry for the interactions of K and eta mesons with pions at low energy. SU(3) chiral symmetry is imposed on the effective field theory by a matching calculation onto three-flavor chiral perturbation theory. The effective Lagrangian for the pi-K and pi-eta sectors is worked out to order Q^4; the effective Lagrangian for the K-K sector is worked out to order Q^2 with contact interactions to order Q^4. As an application of the method, we calculate the K-K s-wave scattering phase shift at leading order and compare with chiral perturbation theory. We conclude with a discussion of the limitations of the approach and propose new directions for work where the matching calculation may be usefulhttps://thesis.library.caltech.edu/id/eprint/3148Photochemical Studies of Jupiter and Titan
https://resolver.caltech.edu/CaltechTHESIS:04262012-150545346
Authors: {'items': [{'id': 'Wong-Ah-San', 'name': {'family': 'Wong', 'given': 'Ah-San'}, 'show_email': 'NO'}]}
Year: 2002
DOI: 10.7907/s8qh-5v68
<p>This study of the atmosphere of Jupiter and Titan consists in large part of three papers, each of which employs the Caltech/ JPL one-dimensional photochemical model.</p>
<p>Paper One: Aromatic compounds have been considered a likely candidate for enhanced aerosol formation in the polar region of Jupiter. In this paper, a new
chemical model for aromatic compounds in the auroral thermosphere/ionosphere is developed, which satisfies constraints from the observations of each of Voyager, Galileo and the Infrared Space Observatory. The study demonstrates that sufficient quantities of higher ring species can condense to form aerosol.</p>
<p>Paper Two: A comprehensive atmospheric model is put forward and used to investigate the details of benzene chemistry on Jupiter, in both its auroral and non-auroral
regions. The benzene formation schemes are discussed for neutral chemistry and ion chemistry, and the major uncertainties in the chemical kinetics are identified.
The model shows that ion chemistry adds an additional source of benzene in auroral regions. The results are compared with observations made by the Infrared Space
Observatory. 172</p>
<p>Paper Three: The recent observation of the heavy isotopomers of CO, ^(13)CO and C^(18)O, may be used to place constraints on the evolution of the atmosphere of Titan. 200 However, the original isotopic signature may be altered by photochemical reactions. This paper explains the absence of C isotopic enrichment in Titan's atmosphere,
despite the significant enrichment of heavy H, N, and O isotopes. It is shown that there is a rapid exchange for C atoms between the CH_4 and CO reservoirs, mediated
by the reaction ^1CH_2+*CO →^1*CH_2 + CO, where *C is ^(13)C. 261 Next, the isotopic dilution of CO is investigated using a photochemical model, the results of
which suggest that the time constant for isotopic exchange through the aforementioned reaction is approximately 800 Myr. This duration is considerably shorter than the age of Titan, and thus any original isotopic enhancement of ^(13)C in CO may have been diluted by this exchange process. This paper concludes by proposing a plausible model for the evolution history of CO on Titan's atmosphere.</p>
https://thesis.library.caltech.edu/id/eprint/6983Entanglement of Multipartite Quantum States and the Generalized Quantum Search
https://resolver.caltech.edu/CaltechTHESIS:01202012-104927686
Authors: {'items': [{'email': 'gingrichca@gmail.com', 'id': 'Gingrich-Robert-Michael', 'name': {'family': 'Gingrich', 'given': 'Robert Michael'}, 'show_email': 'NO'}]}
Year: 2002
DOI: 10.7907/0M1P-NS54
<p>In chapter 2 various parameterizations for the orbits under local unitary transformations of three-qubit pure states are analyzed. It is shown that the entanglement monotones of any multipartite pure state uniquely determine the orbit of that state. It follows that there must be an entanglement monotone for three-qubit pure states which depends on the Kempe invariant defined in [1]. A form for such an entanglement monotone is proposed. A theorem is proved that significantly reduces the number of entanglement monotones that must be looked at to find the maximal probability of transforming one multipartite state
to another.</p>
<p>In chapter 3 Grover's unstructured quantum search algorithm is generalized to use an arbitrary starting superposition and an arbitrary unitary matrix. A formula for the probability of the generalized Grover's algorithm succeeding after n iterations is derived. This formula is used to determine the optimal strategy for using the unstructured quantum search algorithm. The speedup obtained illustrates that a hybrid use of quantum computing and classical computing techniques can yield a performance that is better than either alone. The analysis is extended to the case of a society of k quantum searches acting in parallel.</p>
<p>In chapter 4 the positive map Г : p → (Trρ) - ρ is introduced as a separability criterion. Any separable state is mapped by the tensor product of Г and the identity in to a non-negative operator, which provides a necessary condition for separability. If Г acts on a two-dimensional subsystem, then it is equivalent to partial transposition and therefore also sufficient for 2 x 2 and 2 x 3 systems. Finally, a connection between this map for two qubits and complex conjugation in the "magic" basis [2] is displayed.</p>https://thesis.library.caltech.edu/id/eprint/6769Hyperpolarized Gas Polarimetry and Imaging at Low Magnetic Field
https://resolver.caltech.edu/CaltechETD:etd-05302003-134718
Authors: {'items': [{'email': 'tpavlin@alumni.princeton.edu', 'id': 'Pavlin-Tina', 'name': {'family': 'Pavlin', 'given': 'Tina'}, 'show_email': 'NO'}]}
Year: 2003
DOI: 10.7907/7B1R-3T10
<p>MR imaging with polarized noble gases has shown promise in both, biomedical and material's imaging applications. Its advantage over the conventional proton MRI lies in its ability to produce high signal-to-noise ratio (SNR), high-resolution images at low magnetic field strengths. In this work:</p>
<p>1. We implemented and studied in detail two methods for detecting hyperpolarization levels of 129Xe and 3He: NMR (Nuclear Magnetic Resonance) and EPR (Electron Paramagnetic Resonance). The 3He NMR and EPR data allowed for a comparison of these two polarimetry methods, while 129Xe NMR and EPR data showed promise for the calibration of 129Xe EPR shifts.</p>
<p>2. We investigated the possibility of using a pulsed resistive low-field MR scanner for spin echo imaging of hyperpolarized gases. By collecting CPMG spin echo trains containing 4096 echoes and lasting over 30 seconds, we demonstrated a high degree of stability for the pulsed resistive low-field scanner.</p>
<p>3. We developed a single-shot PGSE sequence for measuring diffusion coefficients of hyperpolarized gases which removed the effects of background gradients, thus allowing a separation of the T2CPMG relaxation from diffusion-induced signal loss. The theoretical estimations of 3He and 129Xe diffusion coefficients which were based on the Lennard-Jones potential agreed well with our measured 3He and 129Xe diffusion coefficients within the experimental errors.</p>
<p>4. We determined the inherent T2 relaxation times of 3He and 129Xe by varying the interecho time in the conventional CPMG spin echo sequence and by modelling the functional dependence of the T2CPMG relaxation time on the interecho spacing.</p>
<p>5. We collected first ever 3He gradient echo images on a pulsed resistive low-field scanner. In addition, we modelled numerically the effects of flip-angle, diffusion and relaxation rates on signal decay during gradient echo imaging with hyperpolarized gases.</p>
<p>6. We show, with simulations and experiments, that central ordering of RARE k-space acquisition significantly reduces diffusion-induced signal loss. The 1-D RARE images of 3He show a factor of a 100 improvement in the SNR (for 1.6 mm resolution) when using centrally ordered phase-encode gradients.</p>https://thesis.library.caltech.edu/id/eprint/2290D-Brane Actions and N=2 Supergravity Solutions
https://resolver.caltech.edu/CaltechETD:etd-06022004-125935
Authors: {'items': [{'id': 'Ciocarlie-Calin-A', 'name': {'family': 'Ciocarlie', 'given': 'Calin A.'}, 'show_email': 'NO'}]}
Year: 2004
DOI: 10.7907/WSR1-2S04
<p>Among the most remarkable recent developments in string theory are the AdS/CFT duality, as proposed by Maldacena, and the emergence of noncommutative geometry. It has been known for some time that for a system of almost coincident D-branes the transverse displacements that represent the collective coordinates of the system become matrix-valued transforming in the adjoint representation of U(N). From a geometrical point of view this is rather surprising but, as we will see in Chapter 2, it is closely related to the noncommutative descriptions of D-branes.</p>
<p>A consequence of the collective coordinates becoming matrix-valued is the appearance of a dielectric effect in which D-branes can become polarized into higher-dimensional fuzzy D-branes. This last aspect has inspired Polchinski and Strassler to find a nonsingular string dual of a confining four-dimensional gauge theory. The nonsingular geometry is sourced by an extended brane arising from Myers' dielectric effect. Following the spirit of the Polchinski-Strassler paper, we find N = 2 supergravity solutions with polarized branes and a field-theory dual. In our case we are able to present exact supergravity solutions by using M-theory reductions to type IIA supergravity.</p>https://thesis.library.caltech.edu/id/eprint/2382Measurement of the Weak Mixing Angle in Møller Scattering
https://resolver.caltech.edu/CaltechETD:etd-04292004-175942
Authors: {'items': [{'id': 'Bega-Klejda-Adnan', 'name': {'family': 'Bega', 'given': 'Klejda Adnan'}, 'show_email': 'NO'}]}
Year: 2004
DOI: 10.7907/HVF5-6787
<p>The weak mixing parameter sin<sup>2</sup>θ<sub>w</sub> is one of the fundamental parameters of the Standard Model. Its tree-level value has been measured with high precision at energies near the Z<sup>0</sup> pole; however, due to radiative corrections at the one-loop level, the value of sin<sup>2</sup>θ<sub>w</sub> is expected to change with the interaction energy. As a result, a measurement of sin<sup>2</sup>θ<sub>w</sub> at low energy (Q<sup>2</sup> << m<sub>Z</sub>, where Q<sup>2</sup> is the momentum transfer and m<sub>Z</sub> is the Z boson mass), provides a test of the Standard Model at the one-loop level, and a probe for new physics beyond the Standard Model.</p>
<p>One way of obtaining sin<sup>2</sup>θ<sub>w</sub> at low energy is from measuring the left-right, parity-violating asymmetry in electron-electron (Møller) scattering: A<sub>PV</sub> = (σ<sub>R</sub>-σ<sub>L</sub>)/(σ<sub>R</sub>+σ<sub>L</sub>), where σ<sub>R</sub> and σ<sub>L</sub> are the cross sections for right and left-handed incident electrons, respectively. The parity violating asymmetry is proportional to the pseudo-scalar weak neutral current coupling in Møller scattering, g<sub>ee</sub>. At tree level g<sub>ee</sub>= 1/4 - sin<sup>2</sup>θ<sub>w</sub>. A precision measurement of the parity-violating asymmetry in Møller scattering was performed by Experiment E158 at the Stanford Linear Accelerator Center (SLAC). During the experiment, ~50 GeV longitudinally polarized electrons scattered off unpolarized atomic electrons in a liquid hydrogen target, corresponding to an average momentum transfer Q<sup>2</sup> ~ 0.03 (GeV/c)<sup>2</sup>. The tree-level prediction for A<sub>PV</sub> at such energy is =~ 300 ppb. However, one-loop radiative corrections reduce its value by ~40%.</p>
<p>This dissertation reports the E158 results from the 2002 data collection period. The parity-violating asymmetry was found to be A<sub>PV</sub> = -160 ± 21 (stat.) ± 17 (syst.) ppb, which represents the first observation of a parity-violating asymmetry in Møller scattering. This value corresponds to a weak mixing angle at Q<sup>2</sup>=0.026 (GeV/c)<sup>2</sup> of sin<sup>2</sup>θ<sub>w</sub> [...] = 0.2379 ± 0.0016 (stat.) ± 0.0013 (syst.), which is -0.3 standard deviations away from the Standard Model prediction: sin<sup>2</sup>θ<sub>w</sub><sup>predicted</sup>[...] = 0.2385 ± 0.0006 (theory). The E158 measurement of sin<sup>2</sup>θ<sub>w</sub> at a precision of δ(sin<sup>2</sup>θ<sub>w</sub>) = 0.0020 provides new physics sensitivity at the TeV scale.</p>
https://thesis.library.caltech.edu/id/eprint/1543Investigations in Quantum Computing: Causality and Graph Isomorphism
https://resolver.caltech.edu/CaltechETD:etd-05272004-174253
Authors: {'items': [{'email': 'dbeckman@toyon.com', 'id': 'Beckman-David-Eugene', 'name': {'family': 'Beckman', 'given': 'David Eugene'}, 'show_email': 'NO'}]}
Year: 2004
DOI: 10.7907/S1R0-0V87
In this thesis I explore two different types of limits on the time complexity of quantum computation---that is, limits on how much time is required to perform a given class of quantum operations on a quantum system. Upper limits can be found by explicit construction; I explore this approach for the problem of determining whether two graphs are isomorphic. Finding lower limits, on the other hand, usually requires appeal to some fundamental principle of the operation under consideration; I use this approach to derive lower limits placed by the requirements of relativistic causality on the time required for implementation of some nonlocal quantum operations. In some situations these limits are attainable, but for other physical spacetime geometries we exhibit classes of operations which do not violate relativistic causality but which are nevertheless not implementable.https://thesis.library.caltech.edu/id/eprint/2139Experiments in Cavity QED: Exploring the Interaction of Quantized Light with a Single Trapped Atom
https://resolver.caltech.edu/CaltechETD:etd-05272005-163452
Authors: {'items': [{'email': 'andreea.boca@jpl.nasa.gov', 'id': 'Boca-Andreea', 'name': {'family': 'Boca', 'given': 'Andreea'}, 'orcid': '0000-0001-6877-7295', 'show_email': 'YES'}]}
Year: 2005
DOI: 10.7907/BK2X-HX12
<p>The experiments discussed in this thesis focus on the interaction of a single trapped atom with the single mode of a high-finesse optical cavity, in the regime of strong coupling.</p>
<p>Chapter 1 gives a brief introduction, after which Chapter 2 describes our recent measurements of the transmission spectrum of the atom-cavity system. The spectrum exhibits a clearly resolved vacuum-Rabi splitting, in good quantitative agreement with theoretical predictions. A new Raman scheme for cooling atomic motion along the cavity axis enables a complete spectrum to be recorded for an individual atom trapped within the cavity mode, in contrast to all previous measurements of this type that have required averaging over 10^3-10^5 atoms.</p>
<p>Chapter 3 discusses our observations of photon blockade for the transmitted light in the presence of one trapped atom. Excitation of the atom-cavity system by a first photon blocks the transmission of a second one, thereby converting an incident Poissonian stream of photons into a sub-Poissonian, anti-bunched stream, as confirmed by measurements of the photon statistics of the transmitted field. The intensity correlations of the cavity transmission also reveal the energy distribution for oscillatory motion of the trapped atom.</p>
<p>Chapter 4 details a set of simple but necessary measurements of relevant experimental parameters such as cavity geometry, linewidth, mirror properties, birefringence, and detection efficiency. The thesis concludes with Appendix A, describing the efficient laser setup we use for our magneto-optical traps.</p>https://thesis.library.caltech.edu/id/eprint/2161Heavy Pentaquarks in the Diquark Model and the Large Nc Expansion
https://resolver.caltech.edu/CaltechETD:etd-05232005-174621
Authors: {'items': [{'id': 'Wessling-Margaret-Ellen', 'name': {'family': 'Wessling', 'given': 'Margaret Ellen'}, 'show_email': 'NO'}]}
Year: 2005
DOI: 10.7907/6812-4G64
<p>Recent experimental evidence for the Θ⁺(1540) has given rise to much theoretical interest in exotic baryons. The Θ⁺ is a baryon that has strangeness S=+1, meaning that it contains an anti-strange quark. Thus it cannot be constructed from three quarks, unlike all other known baryons; it needs at least an extra quark-antiquark pair. It is usually modeled as a pentaquark state in the 10 bar representation of flavor SU(3), with flavor content s̅uudd.</p>
<p>This thesis considers possible heavy pentaquarks, in which the antiquark is charmed or bottom rather than strange. In the context of the diquark model of Jaffe and Wilczek, it is argued that negative-parity pentaquarks of this type may be lighter than their positive-parity counterparts, and hence are likely to be stable against strong decay. Estimates are made for their masses, and their weak decays are discussed. Isospin relations are found between the decay rates for different possible decay channels.</p>
<p>Negative-parity heavy pentaquarks are also considered in a less model-dependent way, in the context of a 1/Nc expansion, where Nc is the number of colors. Heavy quark effective theory is also employed. Mass relations are found between the mass splittings of heavy pentaquarks and those of nonexotic baryons, and SU(3)-breaking corrections to these relations are computed. The results could be helpful in interpreting experimental data if heavy pentaquarks are observed.</p>https://thesis.library.caltech.edu/id/eprint/1976A Search for Cosmic Microwave Background Anisotropies on Arcminute Scales
https://resolver.caltech.edu/CaltechETD:etd-12232007-013248
Authors: {'items': [{'email': 'jack@caltech.edu', 'id': 'Sayers-Jack', 'name': {'family': 'Sayers', 'given': 'Jack'}, 'orcid': '0000-0002-8213-3784', 'show_email': 'YES'}]}
Year: 2008
DOI: 10.7907/2Q9Q-JA33
This thesis describes the results of two sets of observations made in 2003 and 2004 using Bolocam from the Caltech Submillimeter Observatory (CSO), along with a description of the design and performance of the instrument. Bolocam is a large format camera consisting of 144 bolometers with an eight arcminute field of view at the CSO, and can be operated non-simultaneously at 1.1, 1.4, or 2.1 mm. All of the data described in this thesis was collected at 2.1 mm, where the individual beams are approximately one arcminute in size. The observations were made over a total of seventy-nine nights, and consisted of surveys of two science fields, Lynx and the Subaru/XMM Deep Field (SDS1), covering a total area of approximately 1 square degree. The noise properties of the maps are extremely uniform, with RMS variations in coverage of approximately 1.5% for twenty arcsecond map pixels. The point source sensitivity of the maps is approximately 100 μK<sub>CMB</sub> per beam. Fluctuations in emission from the atmosphere limited the sensitivity of our measurements, and several algorithms designed to remove these fluctuations are described. These algorithms also removed astronomical flux, and simulations were used to determine the effect of this attenuation on a CMB power spectrum. Assuming a flat CMB band power in C<sub>ℓ</sub>, our data corresponds to an effective angular multipole of ℓ<sub>eff</sub> = 5700, with a FWHM<sub>ℓ</sub> = 2800. At these scales the CMB power spectrum is expected to be dominated by anisotropies induced by the Sunyaev-Zel'dovich effect (SZE), and have a reasonably flat spectrum. Our data is consistent with a band power of C<sub>ℓ</sub> = 0 μK<sup>2</sup><sub>CMB1</sub>, and an upper limit of C<sub>ℓ</sub> < 755 μK<sup>2</sup><sub>CMB</sub> at a confidence level of 90%. From this result we find that σ<sub>8</sub> < 1.55 at a confidence level of 90%.
https://thesis.library.caltech.edu/id/eprint/5130Search for Signatures of Extra Dimensions in the Diphoton Mass Spectrum with the CMS Detector
https://resolver.caltech.edu/CaltechTHESIS:05182012-101542629
Authors: {'items': [{'email': 'yousimax@gmail.com', 'id': 'Ma-Yousi', 'name': {'family': 'Ma', 'given': 'Yousi'}, 'show_email': 'NO'}]}
Year: 2012
DOI: 10.7907/X33W-ZX56
A search for signatures of extra dimensions in the diphoton invariant-mass spectrum has been performed with the Compact Muon Solenoid detector at the Large Hadron Collider. No excess of events above the standard model expectation is observed using a data sample collected in proton-proton collisions at √s = 7 TeV corresponding to an intergrated luminosity of 2.2 fb<sup>−1</sup>. In the context of the Randall–Sundrum model, lower limits are set on the mass of the first graviton excitation in the range of 0.86–1.84 TeV, for values of the associated coupling parameter k ̃between 0.01 and 0.10. Additionally, in the context of the large-extra-dimensions model, lower limits are set on the effective Planck scale in the range of 2.3–3.8 TeV at the 95% confidence level. These are the most restrictive bounds to date.https://thesis.library.caltech.edu/id/eprint/7046Characterizing a Resonator Bolometer Array
https://resolver.caltech.edu/CaltechTHESIS:05312013-022124797
Authors: {'items': [{'id': 'Wernis-Rebecca-Ann', 'name': {'family': 'Wernis', 'given': 'Rebecca Ann'}, 'show_email': 'NO'}]}
Year: 2013
DOI: 10.7907/XPSC-WR14
High-background applications such as climate monitoring, biology and security applications demand a large dynamic range. Under such conditions ultra-high sensitivity is not required. The resonator bolometer is a novel detector which is well-suited for these conditions. This device takes advantage of the high-density frequency multiplexing capabilities of superconducting microresonators while allowing for the use of high-Tc superconductors in fabrication, which enables a modest (1-4 K) operating temperature and larger dynamic range than is possible with conventional microresonators. The moderate operating temperature and intrinsic multiplexability of this device reduce cost and allow for large pixel counts, making the resonator bolometer especially suitable for the aforementioned applications. A single pixel consists of a superconducting microresonator whose light-absorbing area is placed on a thermally isolated island. Here we present experimental results and theoretical calculations for a prototype resonator bolometer array. Intrinsic device noise and noise equivalent power (NEP) under both dark and illuminated conditions are presented. Under dark conditions the device sensitivity is limited by the thermal noise fluctuations from the bolometer legs. Under the experimental illuminated conditions the device was photon noise limited.https://thesis.library.caltech.edu/id/eprint/7786Nanoelectromechanical Membranes for Multimode Mass Spectrometry
https://resolver.caltech.edu/CaltechTHESIS:05272014-152108855
Authors: {'items': [{'email': 'jarvis.li360@gmail.com', 'id': 'Li-Jarvis', 'name': {'family': 'Li', 'given': 'Jarvis'}, 'show_email': 'YES'}]}
Year: 2014
DOI: 10.7907/R6T2-MP04
Nanoelectromechanical systems (NEMS) represent the next wave in miniaturizing various electrical and mechanical devices used in a variety of fields, such as physics, biology, and engineering. In particular, NEMS devices have high surface area to volume ratios, low power consumption, low mass, and extremely small footprints. These properties allow NEMS to explore more fundamental regimes of matter. Current NEMS mass spectrometry advancements have only utilized doubly-clamped beams and cantilevers. However to expand the measurement capabilities of NEMS mass spectrometry, we utilize a circular membrane geometry in order to build upon the existing measurements in 1 spatial dimension to measure mass spatially in 2-dimensions. Furthermore, membranes should provide a larger potential mass dynamic range. For this experiment, we utilize circular piezoelectric membranes of aluminum nitride and molybdenum stacks. For mass deposition, we utilize a technique known as matrix-assisted laser desorption/ionization (MALDI), which focuses a pulsed UV laser onto the desired sample embedded in a corresponding matrix. The energy causes a plume of particles to desorb off the sample and towards the device. As a particle lands on the device, we are able to deduce its mass from the shift in its resonant frequency. In particular we need to measure the first three resonant frequencies, since the frequency shifts also depend on the location the particle landed on the device. Here we show the viability of our detection setup, mass deposition setup, and our mass deposition results.https://thesis.library.caltech.edu/id/eprint/8400Multi-Model Inference Ranking and Applications to Physics at the Large Hadron Collider
https://resolver.caltech.edu/CaltechTHESIS:06122014-143656852
Authors: {'items': [{'email': 'valerelambert@gmail.com', 'id': 'Lambert-Valere-Regis-Westbrooke', 'name': {'family': 'Lambert', 'given': 'Valere Regis Westbrooke'}, 'show_email': 'YES'}]}
Year: 2014
DOI: 10.7907/43RG-P928
In the measurement of the Higgs Boson decaying into two photons the parametrization of an appropriate background model is essential for fitting the Higgs signal mass peak over a continuous background. This diphoton background modeling is crucial in the statistical process of calculating exclusion limits and the significance of observations in comparison to a background-only hypothesis. It is therefore ideal to obtain knowledge of the physical shape for the background mass distribution as the use of an improper function can lead to biases in the observed limits. Using an Information-Theoretic (I-T) approach for valid inference we apply Akaike Information Criterion (AIC) as a measure of the separation for a fitting model from the data. We then implement a multi-model inference ranking method to build a fit-model that closest represents the Standard Model background in 2013 diphoton data recorded by the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). Potential applications and extensions of this model-selection technique are discussed with reference to CMS detector performance measurements as well as in potential physics analyses at future detectors.https://thesis.library.caltech.edu/id/eprint/8520Magnetic Trapping of Atomic Tritium for Neutrino Mass Measurement
https://resolver.caltech.edu/CaltechTHESIS:07252014-082021105
Authors: {'items': [{'email': 'benjamin.mathias.clark@gmail.com', 'id': 'Clark-Benjamin-Mathias', 'name': {'family': 'Clark', 'given': 'Benjamin Mathias'}, 'show_email': 'NO'}]}
Year: 2014
DOI: 10.7907/N1FG-5H27
Improved measurement of the neutrino mass via β decay spectroscopy requires the development of new energy measurement techniques and a new β decay source. A promising proposal is to measure the β energy by the frequency of the cyclotron radiation emitted in a magnetic field and to use a high purity atomic tritium source. This thesis examines the feasibility of using a magnetic trap to create and maintain such a source. We demonstrate that the loss rate due to β decay heating is not a limiting factor for the design. We also calculate the loss rate due to evaporative cooling and propose that the tritium can be cooled sufficiently during trap loading as to render this negligible. We further demonstrate a design for the magnetic field which produces a highly uniform field over a large fraction of the trap volume as needed for cyclotron frequency spectroscopy while still providing effective trapping.https://thesis.library.caltech.edu/id/eprint/8605New Physics Models in the Diphoton Final State at CMS
https://resolver.caltech.edu/CaltechTHESIS:01152016-102117113
Authors: {'items': [{'email': 'sezata@gmail.com', 'id': 'Wang-Ann-Miao', 'name': {'family': 'Wang', 'given': 'Ann Miao'}, 'show_email': 'NO'}]}
Year: 2015
DOI: 10.7907/Z9CC0XMN
Since the discovery of the Higgs boson at the LHC, its use as a probe to search for beyond the standard model physics, such as supersymmetry, has become important, as seen in a recent search by the CMS experiment using razor variables in the diphoton final state. Motivated by this search, this thesis examines the LHC discovery potential of a SUSY scenario involving bottom squark pair production with a Higgs boson in the final state. We design and implement a software-based trigger using the razor variables for the CMS experiment to record events with a bottom quark-antiquark pair from a Higgs boson. We characterize the full range of signatures at the LHC from this Higgs-aware SUSY scenario and demonstrate the sensitivity of the CMS data to this model.
https://thesis.library.caltech.edu/id/eprint/9535Investigating Quantum Speedups through Numerical Simulations
https://resolver.caltech.edu/CaltechTHESIS:06052017-122137777
Authors: {'items': [{'email': 'shannonawang@yahoo.com', 'id': 'Wang-Shannon', 'name': {'family': 'Wang', 'given': 'Shannon'}, 'orcid': '0000-0003-0585-6556', 'show_email': 'YES'}]}
Year: 2017
DOI: 10.7907/Z9ZP4456
It has been recently noted in a paper by Brandao et al. that the structure of a linear program in a classical semidefinite programming algorithm lends itself to quantization, such that the classical algorithm may experience a quantum speedup if the step of solving a linear program is replaced with the preparation of a Gibbs state of classical Hamiltonian on a quantum computer, where the Hamiltonian is given by a linear combination of the semidefinite program's constraint matrices. The quantum speedup would be exponential if the complexity of the Gibbs sampler used to execute the update step is polynomial in system size. The Gibbs samplers with explicitly defined runtimes are exponential in system size; however, while the quantum Metropolis sampling algorithm by Temme et al. does not have a runtime bounded explicitly in system size, the algorithm heuristically runs in polylogarithmic time. Since the inverse spectral gap of the quantum Metropolis map varies inversely with the running time of the algorithm, we simulate the behavior of the quantum Metropolis map's spectral gap as a function of system size and row sparsity. We also examine how different definitions of fixed row sparsity affect the spectral gap's behavior when the system size is increased linearly. While more numerical evidence is needed to draw a definitive conclusion, the current results appear to indicate that for system sizes ranging from three to ten qubits, if fixed row sparsity is defined as a fixed polynomial function of the system size, then the quantum Metropolis spectral gap behaves as a polynomial function of system size.https://thesis.library.caltech.edu/id/eprint/10282A System for Cancellation of Two-Level System Noise in Kinetic Inductance Devices
https://resolver.caltech.edu/CaltechTHESIS:01282022-221737571
Authors: {'items': [{'email': 'alex.meiburg@gmail.com', 'id': 'Meiburg-Alexander-Heinz', 'name': {'family': 'Meiburg', 'given': 'Alexander'}, 'orcid': '0000-0002-4506-9146', 'show_email': 'YES'}]}
Year: 2018
DOI: 10.7907/372p-e428
Kinetic Inductance Detectors (KIDs) are showing promise in a variety of low-light applications photometry applications, notably in observing B-mode polarization of the cosmic microwave background. These devices are read out by modulating the inductance of an LC resonator through light, and observing the shift in resonant frequency. Among several contributing sources of noise is Two-Level System noise (TLS noise) that causes low-loss drift in the frequency. Under certain assumptions of the source of the noise, we propose a new dual-resonator design that would allow the TLS noise to be observed independently of the signal, and thus cancelled out. This design comes at a roughly factor-of-2 cost in component size and sensitivity. We designed a manufactured a niobium-on-silicon chip, but encountered issues in that we were unable to observe enough TLS noise to conclusively say that the cancellation works.https://thesis.library.caltech.edu/id/eprint/14486Characterization and Improvement of the Thermal Stability of TES Bolometers
https://resolver.caltech.edu/CaltechTHESIS:07182018-144446266
Authors: {'items': [{'email': 'rfsonka@gmail.com', 'id': 'Sonka-Rita-Frances', 'name': {'family': 'Sonka', 'given': 'Rita Frances'}, 'orcid': '0000-0002-1187-9781', 'show_email': 'NO'}]}
Year: 2018
DOI: 10.7907/4v3d-7k67
<p>The successful detection and characterization of the B-modes in the Cosmic Microwave Background (CMB) would dramatically illuminate the physics of the inflationary era. The Observational Cosmology Group is iterating on bolometers in an attempt to detect this signal. The previous detector design became unstable in parts of its transition when adjusted for 220/270 GHz frequencies, limiting its use.</p>
<p>We study the mechanism of instability in these transition edge sensor (TES) bolometers used for ground based observations of the Cosmic Microwave Background (CMB) at 270GHz. The instability limits the range of useful operating resistances of the TES down to ≈50% of the TES normal resistance (R_n), and due to variations in detector properties and optical loading within a column of multiplexed detectors, limits the effective on sky yield to ≈67 %.</p>
<p>Through comparison of 7 new detector thermal capacity designs and measurements of the electrical impedance of the detectors, we show the instability is due to the increased bolometer leg G for higher-frequency detection inducing decoupling of the palladium-gold heat capacity from the thermistor. We demonstrate experimentally that the limiting thermal resistance is due to the small cross sectional area of the silicon nitride bolometer island, and so is easily fixed by layering palladium-gold over an oxide protected TES. The resulting detectors can be biased down to a resistance ≈10% of R<sub>n</sub>, improving the effective on-sky yield to ≈93%.</p>
<p>We also investigate a possibly related, unexpected slope in the Aluminum calibration TES transition and determine that it is not due to phase separation, even accounting for the science TES thermal instability.</p>
https://thesis.library.caltech.edu/id/eprint/11125Search for SUSY with Delayed Photons at the Compact Muon Solenoid
https://resolver.caltech.edu/CaltechTHESIS:05222018-110636485
Authors: {'items': [{'email': 'gillian.kopp@gmail.com', 'id': 'Kopp-Gillian-Baron', 'name': {'family': 'Kopp', 'given': 'Gillian Baron'}, 'orcid': '0000-0001-8160-0208', 'show_email': 'NO'}]}
Year: 2018
DOI: 10.7907/G4D7-G385
The Compact Muon Solenoid (CMS) experiment records data from proton-proton (pp) and heavy ion (Pb-Pb and Pb-p) collisions at the Large Hadron Collider (LHC) to search for physics beyond the Standard Model, test theories of supersymmetry (SUSY), and measure properties of known particles with higher precision. In 2025, the LHC will be upgraded to the High Luminosity LHC (HL-LHC), where the luminosity will be increased by a factor of 10. This will increase the number of pile-up collisions to 140-200 events per proton-proton bunch crossing, compared to the current 40 events per crossing (where each bunch crossing occurs every 25 ns). In order to fully exploit the sensitivity of the CMS experiment, the current detectors must be upgraded to mitigate the effects of the large number of pileup interactions expected in collisions at the HL-LHC. New capabilities, such as precision timing measurements in calorimetric devices and minimum ionizing detectors, have been shown to effectively mitigate the effects due to pileup, and are expected to benefit the overall physics reach of the experiment. In addition to mitigating pileup and increasing the detector capabilities, precision timing is beneficial in the search for particles beyond the Standard Model. A simulation of a benchmark long lived neutralino SUSY search is presented, and it is shown that the generator particle flight times can be faithfully reconstructed using the detector-level information. Identification algorithms for the SUSY model have been significantly improved with the use of a Boosted Decision Tree, and it is demonstrated that this algorithm has many benefits as compared to cut based IDs. With use of the BDT for the long lived neutralino SUSY model, the background rejection is increased significantly, with constant signal acceptance of 53.6%. This is an improvement in the significance of the signal selection by a factor of 2.38. Further improvement is seen with the inclusion of detector timing information in the BDT – with this contributing ≈25% of the information used in signal event identification. We thus demonstrate that with the BDT, the SUSY neutralino search can be performed with increased signal identification significance, and the searches’ sensitivity is expected to improve with the time resolution attained by the upgraded CMS calorimeter. https://thesis.library.caltech.edu/id/eprint/10924Towards High Fidelity Quantum Computation and Simulation with Rydberg Atoms
https://resolver.caltech.edu/CaltechTHESIS:06092020-162351992
Authors: {'items': [{'email': 'anantkale711@gmail.com', 'id': 'Kae-Anant-M', 'name': {'family': 'Kale', 'given': 'Anant M.'}, 'orcid': '0000-0002-7049-5630', 'show_email': 'YES'}]}
Year: 2020
DOI: 10.7907/8mee-md98
Individually trapped neutral atoms are a promising candidate for use in quantum computing and simulation applications. They are highly scalable, have long coherence times and can be entangled via strong dipole-dipole interactions by driving to highly excited Rydberg states. However, the fidelity of single atom operations as well as two-atom entangling operations is limited by intrinsic sources of decoherence such as atomic motion, as well as technical sources of noise such as laser intensity fluctuations and phase/frequency fluctuations. We study the effect of these factors on single atom Rabi oscillations and two-atom Rydberg blockaded Rabi oscillations, using perturbation theory and numerical simulation. We develop a window function approach which helps us qualitatively understand the significance of the different spectral components of the noise as well as quantitatively understand the dependence of the Rabi oscillation fidelity on Rabi frequency. This allows us to predict the maximum experimentally achievable fidelities using independent measurements of experimental parameters such as noise spectra and atomic temperature. Turning to the question of near-term scalability of the experimental system, we prototype and test a method of generating a ’ladder’ configuration of optical tweezers utilizing two independent lasers. Our setup allows us to fully tune the geometry of the ladder, namely the separation between the two rows, the angle between them, and their relative position along the axis of the ladder. This pseudo-2D configuration enables us to reach larger system sizes in the near future and allows us to access beyond 1D physics.https://thesis.library.caltech.edu/id/eprint/13812Gravitational Wave Polarizations: A Test of General Relativity Using Binary Black Hole Mergers
https://resolver.caltech.edu/CaltechTHESIS:08062020-222003579
Authors: {'items': [{'email': 'mathur26sudhi@gmail.com', 'id': 'Mathur-Sudhi', 'name': {'family': 'Mathur', 'given': 'Sudhi'}, 'orcid': '0000-0003-4891-0567', 'show_email': 'NO'}]}
Year: 2020
DOI: 10.7907/q9qa-7770
<p>General Relativity predicts that gravitational radiation is purely tensor polarized and thus, gravitational waves are composed of linear combinations of two transverse polarization modes, referred to as plus (+) and cross (×) tensor modes. However, alternate gravitational theories predict the existence of up to four additional vector and scalar longitudinal GW polarization modes.</p>
<p>In this thesis, we develop a test of the gravitational wave (GW) polarization prediction of general relativity by searching for small admixtures of vector and/or scalar polarization components in transient GWs from binary black hole mergers. We use a network of five non-co-oriented GW detectors available in the near future, Bayesian inference parameter estimation, and nested sampling to quantify the detection sensitivity for such non-tensor GW polarization components.</p>https://thesis.library.caltech.edu/id/eprint/13851Liquid-Induced Discharge of Polypropylene Microfiber Electret Filters
https://resolver.caltech.edu/CaltechTHESIS:06162021-230506010
Authors: {'items': [{'email': 'albertnazeeri@gmail.com', 'id': 'Nazeeri-Albert-Isaac', 'name': {'family': 'Nazeeri', 'given': 'Albert Isaac'}, 'orcid': '0000-0003-0000-9841', 'show_email': 'YES'}]}
Year: 2021
DOI: 10.7907/f88b-x760
<p>Polymer microfiber electret filters are the technology behind N95 and equivalent type respirators. Understanding how liquids interact with and discharge these filters would allow for the development of non-damaging liquid decontamination protocols. Previous work on liquid/filter interactions has been largely empirical with articles reporting the effect a specific liquid has on the filtration efficiency of a particular filter. This thesis proposes a theoretical model of liquid induced discharge of polymer microfiber electret filters via the ideas of surface wetting and electrical conductivity. This model was tested, and validated, on commercially available polypropylene microfiber electret filters through wetting, thermally stimulated discharge (TSD), and filtration experiments.</p>https://thesis.library.caltech.edu/id/eprint/14279A Deep Dive into the Connections Between the Renormalization Group and Deep Learning in the Ising Model
https://resolver.caltech.edu/CaltechTHESIS:05302023-084739008
Authors: {'items': [{'email': 'kelsietaylor137@gmail.com', 'id': 'Taylor-Kelsie-Reed', 'name': {'family': 'Taylor', 'given': 'Kelsie'}, 'orcid': '0009-0001-7510-2306', 'show_email': 'YES'}]}
Year: 2023
DOI: 10.7907/ztpg-z092
The renormalization group (RG) is an essential technique in statistical physics and quantum field theory, which considers scale-invariant properties of physical theories and how these theories’ parameters change with scaling. Deep learning is a powerful computational technique that uses multi-layered neural networks to solve a myriad of complicated problems. Previous research suggests the possibility that unsupervised deep learning may be a form of RG flow, by being a layer-by-layer coarse graining of the original data. We examined this connection on a more rigorous basis for the simple example of Kadanoff block renormalization of the 2D nearest-neighbor Ising model, with our deep learning accomplished via Restricted Boltzmann Machines (RBMs). We developed extensive renormalization techniques for the 1D and 2D Ising model to provide a baseline for comparison. For the 1D Ising model, we successfully used Adam optimization on a correlation length loss function to learn the group flow; yielding results consistent with the analytical model for infinite N. For the 2D Ising model, we successfully generated Ising model samples using the Wolff algorithm, and performed the group flow using a quasi-deterministic method, validating these results by calculating the critical exponent \nu. We then examined RBM learning of the Ising model layer by layer, finding a blocking structure in the learning that is qualitatively similar to RG. Lastly, we directly compared the weights of each layer from the learning to Ising spin renormalization, but found quantitative inconsistencies for the simple case of nearest-neighbor Ising models.https://thesis.library.caltech.edu/id/eprint/15230