Despite the success of the Standard Model of particle physics and the \u03bbCDM model of cosmology in describing many aspects of nature, several fundamental questions still demand extensions of our current understanding. This thesis studies how effective descriptions and symmetry principles can be used to trace possible new physics and understand their effect on low-energy observables.
\r\n\r\nThe first part focuses on large-scale structure as a probe of primordial physics. Since galaxies are biased tracers of the underlying matter density field, extracting primordial information from galaxy surveys requires a controlled treatment of nonlinear gravitational evolution, galaxy bias, and short-distance sensitivity. We study the renormalization of composite operators in the galaxy bias expansion in the presence of local primordial non-Gaussianity, showing how different ultraviolet regulators affect counterterm coefficients while preserving the structures fixed by symmetry.
\r\n\r\nThe second part turns to physics beyond the Standard Model. We study finite naturalness in Pati-Salam theories of quark-lepton unification, deriving constraints from finite threshold corrections to the Higgs mass. We then investigate long-lived axion-like particles in beam-dump experiments, showing that electromagnetic cascades can substantially enhance the sensitivity of such searches. Finally, we study leptogenesis in automatic Nelson-Barr models, identifying viable regions where spontaneous CP violation can both protect the quality of the strong CP solution and generate the observed baryon asymmetry.
\r\n\r\nTogether, these results trace new physics from symmetry to observation, showing how effective descriptions turn microscopic principles into cosmological and experimental targets.
", "doi": "10.7907/74se-jg90", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17365", "collection": "thesis", "collection_id": "17365", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022025-171549960", "primary_object_url": { "basename": "derda_maria.pdf", "content": "final", "filesize": 955707, "license": "other", "mime_type": "application/pdf", "url": "/17365/1/derda_maria.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Soft Theorems from Spontaneous Symmetry Breaking", "author": [ { "family_name": "Derda", "given_name": "Maria Dominika", "orcid": "009-0007-1527-0010", "clpid": "Derda-Maria-Dominika" } ], "thesis_advisor": [ { "family_name": "Cheung", "given_name": "Clifford W.", "orcid": "0000-0002-9983-9425", "clpid": "Cheung-Clifford" } ], "thesis_committee": [ { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" }, { "family_name": "Simmons-Duffin", "given_name": "David", "orcid": "0000-0002-2937-9515", "clpid": "Simmons-Duffin-D" }, { "family_name": "Papucci", "given_name": "Michele", "orcid": "0000-0003-0810-0017", "clpid": "Papucci-Michele" }, { "family_name": "Cheung", "given_name": "Clifford W.", "orcid": "0000-0002-9983-9425", "clpid": "Cheung-Clifford" } ], "local_group": [ { "literal": "Walter Burke Institute for Theoretical Physics" }, { "literal": "div_pma" } ], "abstract": "Spontaneous symmetry breaking occurs when the vacuum state is not preserved under (a subset of) symmetries in the theory. Instead, the symmetry is non-linearly realized by the associated massless degrees of freedom, the Nambu-Goldstone bosons. At the level of on-shell observables, the non-linearly realized symmetry is manifested as a universal structure of scattering amplitudes in the so-called soft limit, which means sending the momenta of a Nambu-Goldstone modes to zero.
\r\n \r\nIn this dissertation, we further explore the link between spontaneous symmetry breaking and infrared dynamics of massless scalars. First, we derive soft theorems for theories with spontaneously broken Poincar\u00e9 symmetries, corresponding to effective field theories for condensed matter systems such as solids, fluids, superfluids, and framids. We also implement a bootstrap in which the enhanced vanishing of amplitudes in the soft limit is taken as an input, thus sculpting out a subclass of exceptional solid, fluid, and framid theories.
\r\n \r\nNext, we consider spontaneous breaking of higher symmetries. We derive a new sub-leading double soft pion theorem in theories with a spontaneously-broken continuous 2-group global symmetry, which intertwines amplitudes with different numbers of pions and photons. We also provide a novel derivation of the leading soft photon theorem from the Ward identity of an emergent 1-form global symmetry in effective field theories where antiparticles are integrated out.
\r\n\r\nFinally, we turn to universal features in low-energy dynamics of generic effective field theories. We extend the scalar geometric soft theorem by allowing the massless scalar to couple to other scalars, fermions, and gauge bosons. The soft theorem keeps its geometric form, but where the field-space geometry now involves the full field content of the theory. As a bonus, we also present novel double soft theorems with fermions, which mimic the geometric structure of the double soft theorem for scalars.
", "doi": "10.7907/0erh-pe17", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17439", "collection": "thesis", "collection_id": "17439", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06092025-224228080", "primary_object_url": { "basename": "testa_adriano_2025.pdf", "content": "final", "filesize": 20747978, "license": "other", "mime_type": "application/pdf", "url": "/17439/1/testa_adriano_2025.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Ripples from the Early Universe to the Present", "author": [ { "family_name": "Testa", "given_name": "Adriano M.", "orcid": "0000-0003-4423-9243", "clpid": "Testa-Adriano-M" } ], "thesis_advisor": [ { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" } ], "thesis_committee": [ { "family_name": "Porter", "given_name": "Frank C.", "orcid": "0000-0003-1948-8889", "clpid": "Porter-F-C" }, { "family_name": "Dor\u00e9", "given_name": "Olivier P.", "orcid": "0000-0001-7432-2932", "clpid": "Dor\u00e9-O" }, { "family_name": "Papucci", "given_name": "Michele", "orcid": "0000-0003-0810-0017", "clpid": "Papucci-Michele" }, { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "In this thesis we study a range of topics in cosmology and gravitational wave physics, emphasizing their roles as probes of fundamental physics across vastly different scales. On the cosmology side, we focus on the analysis of the bispectrum, which provides unique insights into the physics of the early universe. Our work includes a calculation of the bispectrum in the squeezed-limit in quasi-single field inflation using Conformal Fermi Coordinates, a demonstration of the equivalence of different regularization prescriptions for the galaxy bias expansion, and the first numerical evaluation of the bispectrum in the Spherical Fourier-Bessel basis. On the gravitational wave side, we present an analytical template for the ring-down signal from rotating exotic compact objects, with applications to searches in interferometer data.", "doi": "10.7907/1664-d461", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16320", "collection": "thesis", "collection_id": "16320", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03072024-065323362", "primary_object_url": { "basename": "main.pdf", "content": "final", "filesize": 92470516, "license": "other", "mime_type": "application/pdf", "url": "/16320/1/main.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Search for New Physics with the Compact Muon Solenoid Experiment and QIS-enabled Technology", "author": [ { "family_name": "Wang", "given_name": "Christina Wenlu", "orcid": "0000-0002-0117-7196", "clpid": "Wang-Christina-Wenlu" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Filippone", "given_name": "Bradley W.", "orcid": "0000-0002-2618-2688", "clpid": "Filippone-B-W" }, { "family_name": "Papucci", "given_name": "Michele", "orcid": "0000-0003-0810-0017", "clpid": "Papucci-Michele" }, { "family_name": "Cheung", "given_name": "Clifford W.", "orcid": "0000-0002-9983-9425", "clpid": "Cheung-Clifford" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Understanding the fundamental nature of dark matter (DM) — its cosmological origin, constituents, and interactions — is one of the most important questions in fundamental science today. In this thesis, I present two novel and highly complementary approaches to cover the gaps in sensitivity of current DM searches. The searches are enabled by a first-of-its-kind reconstruction technique to search for hidden-sector particles using the Compact Muon Solenoid (CMS) and by new advances in quantum sensing technology to search for axions and hidden-sector DM.
\r\n\r\nIn the first part of this thesis, I present a search for long-lived hidden sector particles, predicted by many extensions of the SM, using a novel technique to reconstruct decays of long-lived particles (LLPs) in the CMS muon detector. The innovative LLP reconstruction technique is sensitive to a broad range of LLP decays and to LLP masses below GeV. The search yields competitive sensitivity for proper lifetime 0.1 - 1000 m with the full Run 2 dataset recorded at the LHC between 2016 - 2018 at √s = 13 TeV. To extend the physics reach of this novel muon detector shower (MDS) signature, I present the model-independence of MDS and the reinterpretation of the search to a large number of LLP models, demonstrating its complementarity with proposed and existing dedicated LLP experiments. Finally, I present a new dedicated MDS trigger that improves the trigger efficiency by at least an order of magnitude and was deployed in 2022, at the start of Run 3 of the LHC operations.
\r\n\r\nIn the second part of the thesis, I present for the first time, the use of a novel quantum sensor, the low-noise and single-photon sensitive superconducting nanowire single photon detectors (SNSPDs), to directly detect dark matter. The low detection threshold and ultra-low dark count rate of SNSPDs can close the gap in DM discovery reach due to the current limitations in detector sensitivity. I will present my work on the development and characterization of SNSPDs for two entirely new experiments to directly detect axions via absorption and hidden-sector DM via electron scattering. The search for axions employs a novel broadband reflector technique with the Broadband Reflector Experiment for Axion Detection (BREAD). A unique parabolic mirror is then used to focus axion-converted photons to the SNSPDs, extending the reach to axion masses of 0.04 - 1 eV. On the other hand, by coupling the SNSPDs with gallium arsenide, a bright cryogenic scintillator well matched to SNSPD detection, a prototype sensing system can be built as a basis of new direct DM detection experiments capable of extending the discovery to DM masses as low as 1 MeV.
", "doi": "10.7907/ta74-mz22", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" } ]