Cosmological and astrophysical probes of axionlike particles

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dc.contributor.advisorLong, Andrew Jen_US
dc.contributor.advisorAmin, Mustafa Aen_US
dc.creatorHagimoto, Ray Mitchellen_US
dc.date.accessioned2025-01-17T17:42:33Zen_US
dc.date.available2025-01-17T17:42:33Zen_US
dc.date.created2024-12en_US
dc.date.issued2024-12-06en_US
dc.date.submittedDecember 2024en_US
dc.date.updated2025-01-17T17:42:33Zen_US
dc.description.abstractAxionlike particles (ALPs), pseudo Nambu-Goldstone bosons arising from the spontaneous breaking of global U(1) symmetries, appear in solutions to open issues in fundamental physics and are ubiquitous in string theory compactifications. Furthermore, ALPs have a rich phenomenology that provides numerous ways to search for evidence of their existence. This work explores two potential discovery channels for ALPs. The first considers the possibility that hyperlight ALPs, with masses less than 10^(-28) eV and a Chern-Simons coupling to electromagnetism, formed a cosmic string network in the early Universe that survives beyond recombination. In this scenario, cosmic microwave background (CMB) photons passing through string loops in the network experience a rotation in their plane of polarization, an effect known as CMB birefringence that may be within reach of future CMB probes. I use existing CMB birefringence power spectrum data to constrain axion string network parameters, then discuss non-Gaussian features of axion string-induced CMB birefringence maps, and finally explore how a neural network could estimate axion string network parameters from these maps. The second potential discovery channel examines how ALPs with lepton flavor-violating couplings and masses less than 1 MeV affect the cooling rates of neutron stars. Through these studies, I develop tools that would assist in identifying signatures of ALPs in cosmological and astrophysical observations.en_US
dc.format.mimetypeapplication/pdfen_US
dc.identifier.urihttps://hdl.handle.net/1911/118243en_US
dc.language.isoenen_US
dc.subjectaxionsen_US
dc.subjectcosmologyen_US
dc.subjectaxionlikeparticlesen_US
dc.subjectbirefringenceen_US
dc.subjectcosmic microwave backgrounden_US
dc.subjectphysicsen_US
dc.subjectphenomenologyen_US
dc.titleCosmological and astrophysical probes of axionlike particlesen_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentPhysics and Astronomyen_US
thesis.degree.disciplinePhysicsen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophyen_US
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