Hartree-Fock (HF) calculations have had remarkable success in describing large nuclei at\r\nhigh spin, temperature and deformation. To allow full range of possible deformations,\r\nthe Skyrme HF equations can be discretized on a three-dimensional mesh. However, such\r\ncalculations are currently limited by the computational resources provided by traditional\r\nsupercomputers. To take advantage of recent developments in massively parallel computing\r\ntechnology, we have implemented the LLNL Skyrme-force static and rotational\r\nHF codes on Intel's DELTA and GAMMA systems at Caltech.

\r\n\r\nWe decomposed the HF code by assigning a portion of the mesh to each node, with\r\nnearest neighbor meshes assigned to nodes connected by communication\u00b7 channels. This\r\nkind of decomposition is well-suited for the DELTA and the GAMMA architecture because\r\nthe only non-local operations are wave function orthogonalization and the boundary\r\nconditions of the Poisson equation for the Coulomb field.

\r\n\r\nOur first application of the HF code on parallel computers has been the study of\r\nidentical superdeformed (SD) rotational bands in the Hg region. In the last ten years,\r\nmany SD rotational bands have been found experimentally. One very surprising feature\r\nfound in these SD rotational bands is that many pairs of bands in nuclei that differ\r\nby one or two mass units have nearly identical deexcitation gamma-ray energies. Our\r\ncalculations of the five rotational bands in ^(192)Hg and ^(194)Pb show that the filling of\r\nspecific orbitals can lead to bands with deexcitation gamma-ray energies differing by at\r\nmost 2 keV in nuclei differing by two mass units and over a range of angular momenta comparable to that observed experimentally. Our calculations of SD rotational bands\r\nin the Dy region also show that twinning can be achieved by filling or emptying some specific orbitals.

\r\n\r\nThe interpretation of future precise experiments on atomic parity nonconservation\r\n(PNC) in terms of parameters of the Standard Model could be hampered by uncertainties\r\nin the atomic and nuclear structure. As a further application of the massively parallel\r\nHF calculations, we calculated the proton and neutron densities of the Cesium isotopes\r\nfrom A = 125 to A = 139. Based on our good agreement with experimental charge\r\nradii, binding energies, and ground state spins, we conclude that the uncertainties in\r\nthe ratios of weak charges are less than 10^(-3), comfortably smaller than the anticipated experimental error.

", "doi": "10.7907/kp30-db55", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:8037", "collection": "thesis", "collection_id": "8037", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12042013-111115672", "primary_object_url": { "basename": "Muller_hm_1999.pdf", "content": "final", "filesize": 26893722, "license": "other", "mime_type": "application/pdf", "url": "/8037/1/Muller_hm_1999.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Fermionic quantum systems. Part I: Phase transitions in quantum dots. Part II: Nuclear matter on a lattice", "author": [ { "family_name": "M\u00fcller", "given_name": "Hans-Michael", "clpid": "M\u00fcller-H-M" } ], "thesis_advisor": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "In the first part I perform Hartree-Fock calculations to show that quantum dots (i.e.,\r\ntwo-dimensional systems of up to twenty interacting electrons in an external parabolic\r\npotential) undergo a gradual transition to a spin-polarized Wigner crystal with increasing\r\nmagnetic field strength. The phase diagram and ground state energies have\r\nbeen determined. I tried to improve the ground state of the Wigner crystal by introducing\r\na Jastrow ansatz for the wave function and performing a variational Monte\r\nCarlo calculation. The existence of so called magic numbers was also investigated.\r\nFinally, I also calculated the heat capacity associated with the rotational degree of\r\nfreedom of deformed many-body states and suggest an experimental method to detect\r\nWigner crystals.

\r\n\r\nThe second part of the thesis investigates infinite nuclear matter on a cubic lattice.\r\nThe exact thermal formalism describes nucleons with a Hamiltonian that accommodates\r\non-site and next-neighbor parts of the central, spin-exchange and isospin-exchange\r\ninteraction. Using auxiliary field Monte Carlo methods, I show that energy\r\nand basic saturation properties of nuclear matter can be reproduced. A first order\r\nphase transition from an uncorrelated Fermi gas to a clustered system is observed\r\nby computing mechanical and thermodynamical quantities such as compressibility,\r\nheat capacity, entropy and grand potential. The structure of the clusters is investigated\r\nwith the help two-body correlations. I compare symmetry energy and first\r\nsound velocities with literature and find reasonable agreement. I also calculate the\r\nenergy of pure neutron matter and search for a similar phase transition, but the survey\r\nis restricted by the infamous Monte Carlo sign problem. Also, a regularization\r\nscheme to extract potential parameters from scattering lengths and effective ranges\r\nis investigated.

", "doi": "10.7907/yznz-2b69", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:10747", "collection": "thesis", "collection_id": "10747", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03022018-134310889", "type": "thesis", "title": "Application of TDHF Methods to Nuclear Physics", "author": [ { "family_name": "Flanders", "given_name": "Bradley A.", "clpid": "Flanders-Bradley-A" } ], "thesis_advisor": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" } ], "thesis_committee": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Fox", "given_name": "Geoffrey C.", "clpid": "Fox-G-C" }, { "family_name": "Devi", "given_name": "K. R. Sandhya", "clpid": "Devi-K-R-Sandhya" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Part I presents results for TDHF calculations of realistic heavy-ion reactions. Results for a separable approximation, neglecting motion normal to the scattering plane, agree very well with the results of the full 3-D calculation. Results for the fusion cross section of two systems leading to the compound nucleus ^{56}Ni are compared with experimental data. The ^{16}O + ^{40}Ca results agree quite well with the experimental data, and the ^{28}Si + ^{28}Si results agree quite well with experimental data for the similar ^{32}S + ^{27}Al system. Results of calculations with the separable approximation for ^{86}Kr + ^{139}La are compared with both axially symmetric calculations and experimental results. All three show substantial agreement.

Part II presents a stability criterion for the validity of TDHF solutions based on a time-dependent generalization of RPA theory. Results are tested in an exactly soluble model, the SU(3) generalization of the Lipkin model. Unfortunately, the exact solution could not be computed for a large enough number of particles to permit quantitative testing of this criterion. However, it does seem to correctly indicate the stability or instability of the TDHF path.

", "doi": "10.7907/vakw-ws15", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:11335", "collection": "thesis", "collection_id": "11335", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01072019-110818820", "primary_object_url": { "basename": "Sugiyama_G_1985.pdf", "content": "final", "filesize": 42823779, "license": "other", "mime_type": "application/pdf", "url": "/11335/1/Sugiyama_G_1985.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Auxiliary Field Monte-Carlo for Quantum Many-Body Systems", "author": [ { "family_name": "Sugiyama", "given_name": "Gayle A.", "clpid": "Sugiyama-Gayle-A" } ], "thesis_advisor": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" } ], "thesis_committee": [ { "family_name": "Barnes", "given_name": "Charles A.", "clpid": "Barnes-C-A" }, { "family_name": "Fox", "given_name": "Geoffrey C.", "clpid": "Fox-G-C" }, { "family_name": "Cross", "given_name": "Michael Clifford", "clpid": "Cross-M-C" }, { "family_name": "Frautschi", "given_name": "Steven C.", "clpid": "Frautschi-S-C" }, { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "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.

", "doi": "10.7907/t9kp-qe57", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:11406", "collection": "thesis", "collection_id": "11406", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02202019-120226199", "primary_object_url": { "basename": "Meredith_DC_1987.pdf", "content": "final", "filesize": 56426474, "license": "other", "mime_type": "application/pdf", "url": "/11406/1/Meredith_DC_1987.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Quantum Chaos: Spectral Fluctuations and Overlap Distributions of the Three Level Lipkin-Meshkov-Glick Model", "author": [ { "family_name": "Meredith", "given_name": "Dawn Christine", "clpid": "Meredith-Dawn-Christine" } ], "thesis_advisor": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" } ], "thesis_committee": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" }, { "family_name": "Marcus", "given_name": "Rudolph A.", "clpid": "Marcus-R-A" }, { "family_name": "Simon", "given_name": "Barry M.", "clpid": "Simon-B-M" }, { "family_name": "Wise", "given_name": "Mark B.", "clpid": "Wise-M-B" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "We test the prediction that quantum systems with chaotic classical analogs have spectral fluctuations and overlap distributions equal to those of the Gaussian Orthogonal Ensemble (GOE). The subject of our study is the three level Lipkin-Meshkov-Glick model of nuclear physics. This model differs from previously investigated systems because the quantum basis and classical phase space are compact, and the classical Hamiltonian has quartic momentum dependence. We investigate the dynamics of the classical analog to identify values of coupling strength and energy ranges for which the motion is chaotic, quasi-chaotic, and quasi-integrable. We then analyze the fluctuation properties of the eigenvalues for those same energy ranges and coupling strength, and we find that the chaotic eigenvalues are in good agreement with GOE fluctuations, while the quasi-integrable and quasichaotic levels fluctuations are closer to the Poisson fluctuations that are predicted for integrable systems. We also study the distribution of the overlap of a chaotic eigenvector with a basis vector, and find that in some cases it is a Gaussian random variable as predicted by GOE. This result, however, is not universal.

\r\n", "doi": "10.7907/7y5k-ex17", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:11840", "collection": "thesis", "collection_id": "11840", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10222019-115047089", "type": "thesis", "title": "Two Problems in Many Body Physics: I. Photon Production: A Probe of Heavy Ion Collisions. II. Structure of Matter in Strong Magnetic Fields", "author": [ { "family_name": "Neuhauser", "given_name": "Daniel", "clpid": "Neuhauser-Daniel" } ], "thesis_advisor": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" } ], "thesis_committee": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Newman", "given_name": "Harvey B.", "clpid": "Newman-H-B" }, { "family_name": "Goodstein", "given_name": "David L.", "clpid": "Goodstein-D-L" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "In Part 1 we examine the theoretical framework for the use of photon spectra to probe heavy ion collisions. We first calculate single photon emission spectra from nuclear matter in the incoherent limit and combine them with the simplified participant-spectator model and with the semiclassical VUU model, to predict photon production cross sections in heavy ion collisions. The spectra differ from previous estimates based on a classical soft-photon approximation and lead to good agreement with experiment, except for an overall normalization factor of order (2-5), which we interpret as direct evidence for medium effects.

\r\n\r\nWe then proceed to examine the Hanbury-Brown-Twiss correlation of high-energy photons emitted from heavy ion collisions. We find that both the polarization average and a possible coherent component complicate the extraction of the size and lifetime of the emitting source from the correlation function.

\r\n\r\nIn Part 2 we calculate the binding energies of atoms and molecular chains in 10^{12} G magnetic fields using the Hartree-Fock method. Our calculations are the first self-consistent ones treating exchange properly for atoms heavier than helium in high fields. For *Z* > 2 at 10^{12}G and *Z* > 4 at 5 x 10^{12}G the isolated atom is energetically favored over the molecular chains.

We construct an eigenvalue problem by confining many-body system to a bounded domain with the boundary condition that the wave function vanishes. By changing the boundary, however, the eigenvalues of the energy can be varied continuously. The D-matrix is defined for a series of bounded problems with the same value for the ground state energy. The D-matrix is related to the S-matrix, enabling us to calculate the S-matrix at a given energy. The Schrodinger equation for the system is transformed to a diffusion equation by regarding time as imaginary. Initial ensemble, representing an approximate wave function, is evolved, through Monte Carlo simulation of random walks and branching, to the ground state ensemble. The limitations of investigation are: 1. Ingoing and outgoing channels have two fragments. 2. The interaction between the fragments is negligible outside the boundary mentioned above. 3. The particles are bosons or we know the zeros of the wave function.

\r\n\r\nFirst we consider the scattering of a particle by a potential, which is equivalent to the two-body problem, in one dimension. Here we use the Poschl-Teller potential for which the exact solution is known. We use this case to investigate a new sampling method and study of various parameters. Next we consider three particles in one dimension. Here we take interaction to be a potential well, where at least one of the interactions is attractive so that a two-body bound state is possible.

", "doi": "10.7907/09kg-d808", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:11828", "collection": "thesis", "collection_id": "11828", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10182019-162452942", "type": "thesis", "title": "Realistic Calculations of Excitations in Nuclear Matter", "author": [ { "family_name": "Kwong", "given_name": "Nai-Hang", "clpid": "Kwong-Nai-Hang" } ], "thesis_advisor": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" } ], "thesis_committee": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" }, { "family_name": "Frautschi", "given_name": "Steven C.", "clpid": "Frautschi-S-C" }, { "family_name": "Barnes", "given_name": "Charles A.", "clpid": "Barnes-C-A" }, { "family_name": "Vogel", "given_name": "Petr", "clpid": "Vogel-P" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "A numerical method has been developed to solve the RPA equation, exchange term included, in nuclear matter. The dynamic form factor S(q, \u03c9) 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 ^{3}He and the microscopic calculation of Landau parameters.

We formulate the quasielastic response of a non-relativistic many-body system at zero temperature in terms of ground state density matrix elements and real time path integrals that embody the final state interactions. While the former provide the weight for a conventional Monte Carlo calculation, the latter require a more sophisticated treatment. We argue that the recently developed Stationary Phase Monte Carlo technique can be used to study the approach to \"Y-scaling.\" We perform calculations for a particle in a potential well in one and three dimensions and compare them to the exact results available for these models. We then derive an eikonal approximation to the Path Integrals. This method is suitably generalized to treat strongly repulsive interactions, and allows comparison to Silver's theory of final state interactions in a straightforward way. We also give an exact prescription to calculate the scaling limit for potentials comprising a hard core. Finally, we study the approach to scaling in a model \u2074He nucleus, and find good agreement with experimental data.

", "doi": "10.7907/mkyz-4067", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:5323", "collection": "thesis", "collection_id": "5323", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10222009-160215418", "primary_object_url": { "basename": "Lang_ghw_1993.pdf", "content": "final", "filesize": 3423271, "license": "other", "mime_type": "application/pdf", "url": "/5323/1/Lang_ghw_1993.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Auxiliary-field Monte Carlo methods for interacting fermions : application to the nuclear shell model", "author": [ { "family_name": "Lang", "given_name": "Gladys Hau-Wan", "clpid": "Lang-G-H-W" } ], "thesis_advisor": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" }, { "family_name": "Goddard", "given_name": "William A., III", "clpid": "Goddard-W-A-III" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis presents the path-integral formulation of the nuclear shell model using the Hubbard-Stratonovich transformation, which linearizes the two-body interaction by auxiliary fields. The path-integral was evaluated via Monte Carlo. The method scales favorably with valence-nucleon number and shell-model basis: full-basis calculations can be done up to the rare-earth region, which cannot be treated by other methods. Observables are calculated for the ground state and in a thermal \r\nensemble. Dynamical correlations are obtained, from which strength functions are extracted through the Maximum Entropy method. Examples in the s-d shell, where exact diagonalization can be carried out, compare well with exact results. The \"sign problem\", which is generic to fermion Monte Carlo calculations, is proved to be absent in a wide class of interactions including the attractive pairing-plus-multipole interactions. The formulation is general for interacting fermion systems and is well suited for parallel computation. The method has been implemented on the Intel Touchstone Delta System, achieving better than 99% parallelization.\r\n", "doi": "10.7907/xh84-k642", "publication_date": "1993", "thesis_type": "phd", "thesis_year": "1993" }, { "id": "thesis:11780", "collection": "thesis", "collection_id": "11780", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08302019-142642675", "primary_object_url": { "basename": "Chu_MC_1987.pdf", "content": "final", "filesize": 35117563, "license": "other", "mime_type": "application/pdf", "url": "/11780/1/Chu_MC_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Hydrodynamics of Ultra-Relativistic Heavy-Ion Collisions", "author": [ { "family_name": "Chu", "given_name": "Ming-chung", "clpid": "Chu-Ming-chung" } ], "thesis_advisor": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" } ], "thesis_committee": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" }, { "family_name": "Filippone", "given_name": "Bradley W.", "clpid": "Filippone-B-W" }, { "family_name": "Newman", "given_name": "Harvey B.", "clpid": "Newman-H-B" }, { "family_name": "Zachariasen", "given_name": "Fredrik", "clpid": "Zachariasen-F" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Relativistic hydrodynamic calculations are presented to describe the dynamics\r\nof ultra-relativistic heavy-ion collisions. In contrast to the \"standard picture\" of\r\nthe field, our calculations do not assume scaling symmetry, and in fact we find\r\nlarge scaling violations near the fragmentation regions. In our 1+1-dimensional\r\ncalculations, we find that while the hydrodynamic evolution is very sensitive to the\r\nformation and thermalization time and to the models of the source terms, the effects\r\nof changing the viscosity and the equation of state are small. Our 2+1-dimensional\r\ncalculations show that transverse expansion is not important in the central rapidity\r\nregion. We also present a brief review of the proposed signatures of the formation of\r\nquark-gluon plasma in high energy heavy-ion collisions, as examples of applications\r\nof hydrodynamics.

", "doi": "10.7907/kq9w-6f74", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:5966", "collection": "thesis", "collection_id": "5966", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06302010-080153741", "primary_object_url": { "basename": "Ponisch_v_1986.pdf", "content": "final", "filesize": 3944664, "license": "other", "mime_type": "application/pdf", "url": "/5966/1/Ponisch_v_1986.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Subbarier Fusion of the Oxygen Isotopes", "author": [ { "family_name": "P\u00f6nisch", "given_name": "Volker", "clpid": "P\u00f6nisch-Volker" } ], "thesis_advisor": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" } ], "thesis_committee": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" }, { "family_name": "Barnes", "given_name": "Charles A.", "clpid": "Barnes-C-A" }, { "family_name": "Prince", "given_name": "Thomas A.", "clpid": "Prince-T-A" }, { "family_name": "Politzer", "given_name": "Hugh David", "clpid": "Politzer-H-D" }, { "family_name": "Winther", "given_name": "Aage", "clpid": "Winther-Aage" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "The subbarrier fusion process is studied for systems involving oxygen isotopes. A one-channel incoming wave boundary condition (IWBC) calculation gives an excellent fit to fusion cross section data for ^{16}O+^{16}O. An IWBC coupled channels calculation for ^{17}O+^{16}O that includes inelastic excitations as well as one-neutron transfer with formfactors calculated in a consistent single-particle framework reproduces the subbarrier enhancement down to four fifths the barrier height, but not below that. The calculation does not invoke the adiabatic approximation, which would create non-unitarity in the coupled channels equations. The measured subbarrier fusion cross section for ^{18}O+^{16}O is well reproduced by an IWBC coupled channels calculation with two-neutron transfer, but the calculation disagrees with the above-barrier data.

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.

", "doi": "10.7907/ezwt-k047", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:11879", "collection": "thesis", "collection_id": "11879", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10312019-172947012", "primary_object_url": { "basename": "Bahukutumbi_RP_1996.pdf", "content": "final", "filesize": 25893475, "license": "other", "mime_type": "application/pdf", "url": "/11879/1/Bahukutumbi_RP_1996.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Shell Model Monte Carlo for Gamow-Teller Strengths and Two-Neutrino Double Beta Decay", "author": [ { "family_name": "Bahukutumbi", "given_name": "Radha Pillapakkam", "clpid": "Bahukutumbi-Radha-Pillapakkam" } ], "thesis_advisor": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" } ], "thesis_committee": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" }, { "family_name": "Cross", "given_name": "Michael Clifford", "clpid": "Cross-M-C" }, { "family_name": "Hughes", "given_name": "Emlyn Willard", "clpid": "Hughes-Emlyn-Willard" }, { "family_name": "Vogel", "given_name": "Petr", "clpid": "Vogel-P" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "In this thesis, a method to calculate two-neutrino double beta decay matrix elements employing the Shell Model Monte Carlo is presented. This method is validated against direct-diagonalization for the decay of ^{48}Ca. The first realistic calculation of the nuclear matrix element within the shell model for ^{76}Ge is performed; the result is in reasonable agreement with experiment.

The sensitivity of the shell model results to the nuclear Hamiltonian has been studied for the case of ^{48}Ca where the Hamiltonian used is known to be an optimal one. While one cannot make the nuclear matrix element arbitrarily small, the uncertainty in certain pieces of the Hamiltonian such as the monopole isovector pairing, provides room for at least a factor of two in the matrix element (and hence a factor of four in the half-life) from such calculations.

A Maximum Entropy method to obtain realistic strength functions from imaginary time response functions has been applied to Gamow-Teller response functions calculated using the Shell Model Monte Carlo and the results are validated against direct-diagonalization and experiment.

\r\n\r\nFuture prospects for double beta decay calculations and astrophysical applications of the Gamow-Teller strength functions are briefly discussed.

", "doi": "10.7907/xg95-wy83", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:6198", "collection": "thesis", "collection_id": "6198", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12082010-110205851", "type": "thesis", "title": "A Proximity Formulation of Nuclear Dynamics", "author": [ { "family_name": "Ball", "given_name": "Gregory John", "clpid": "Ball-Gregory-John" } ], "thesis_advisor": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" } ], "thesis_committee": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" }, { "family_name": "Barnes", "given_name": "Charles A.", "clpid": "Barnes-C-A" }, { "family_name": "Friedrich", "given_name": "Harald S. W.", "clpid": "Friedrich-Harald-S-W" }, { "family_name": "Zachariasen", "given_name": "Fredrik", "clpid": "Zachariasen-F" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "The nuclear potential, the transfer-induced dissipation, and the mass diffusion coefficient in heavy-ion collisions are investigated in a proximity formulation. An energy-dependent nuclear potential is calculated in the frozen wave function approximation using two slabs of symmetric nuclear matter, each described by Hartree-Fock single-particle wave functions. Corrections to the inertia parameter are also evaluated from this potential. The flux entering the window formula for the friction between two heavy ions is calculated in a simple barrier penetration model. The classically forbidden flux is found to make a significant contribution. The transfer flux arising from both the relative motion and finite temperature of the nuclei is calculated and the latter is used to estimate the mass diffusion coefficient. Using the mean trajectories from time-dependent Hartree-Fock calculations the charge variance is calculated for the reaction ^{84}Kr(712 MeV) + ^{209}Bi and is found to be in agreement with experiment.

We study the phenomenon of y-scaling in inclusive quasielastic electron scattering. Emphasis is placed on the approach to scaling at finite four-momentum transfers, and the effects of final state interactions. Brueckner-Goldstone perturbation theory for nuclear matter is used to perform a detailed, microscopic calculation of the dynamic structure function of nuclear matter. This is compared to the naive prediction of the Impulse approximation, and we find that the approach to scaling is quite different. The Brueckner-Goldstone approach reproduces the trends seen experimentally (Impulse approximation does not); however, there is still not good quantitative agreement with the data. We take this to be a possible sign of problems in the conventional nucleon-nucleon interactions studied.

", "doi": "10.7907/pp3m-h071", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:8785", "collection": "thesis", "collection_id": "8785", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03182015-112613348", "primary_object_url": { "basename": "Wasson-da-1990.pdf", "content": "final", "filesize": 42432874, "license": "other", "mime_type": "application/pdf", "url": "/8785/1/Wasson-da-1990.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Relativistic mean field theory: methods and applications", "author": [ { "family_name": "Wasson", "given_name": "David Allan", "clpid": "Wasson-D-A" } ], "thesis_advisor": [ { "family_name": "Koonin", "given_name": "Steven E.", "clpid": "Koonin-S-E" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "We develop a method for performing one-loop calculations in finite systems that is based on using the WKB approximation for the high energy states. This approximation allows us to absorb all the counterterms analytically and thereby avoids the need for extreme numerical precision that was required by previous methods. In addition, the local approximation makes this method well suited for self-consistent calculations. We then discuss the application of relativistic mean field methods to the atomic nucleus. Self-consistent, one loop calculations in the Walecka model are performed and the role of the vacuum in this model is analyzed. This model predicts that vacuum polarization effects are responsible for up to five percent of the local nucleon density. Within this framework the possible role of strangeness degrees of freedom is studied. We find that strangeness polarization can increase the kaon-nucleus scattering cross section by ten percent. By introducing a cutoff into the model, the dependence of the model on short-distance physics, where its validity is doubtful, is calculated. The model is very sensitive to cutoffs around one GeV.

\r\n", "doi": "10.7907/gs6h-m244", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" } ]