Search

The particle nature of dark matter and its interactions are issues of central importance with the current understanding of particle physics and clearly indicate the need to go beyond the Standard Model. The lack of detection of a WIMP has spurred both experimental and theoretical innovation. A wide array of direct and indirect detection techniques have vastly expanded the experimentally probed parameter space. This includes small tabletop experiments, large underground detectors, and ground- and space-based telescopes searching for astrophysical and cosmological signals. In conjunction, theorists have gone beyond the standard dark matter scenario by adding new fields, interactions, and portals connecting to the Standard Model. The rich phenomenology associated with these models predict novel signatures and the experimental data provide exciting avenues to search for signs of new physics. In this dissertation, we present progress on exploring dark sector and BSM phenomenology from various lenses. In the most dire scenarios, dark matter does not couple to the Standard Model and only possesses self-interactions. Despite this, the underlying interactions produce cross sections which exhibit significantly different behaviors as a function of velocity. We develop a formalism to compute the cross section, that carefully matches the effective quantum mechanics and QFT descriptions, and takes into account Sommerfeld enhancement, a non-perturbative effect relevant in the nonrelativistic regime. We find that pseudoscalar and axial-vector type interactions don't exhibit this enhancement. This formalism consistently deals with the pseudoscalar potential, which a priori seems singular. This leads us to propose the Quantum Mechanics Swampland, where we begin to delineate the boundary between quantum mechanical potentials which can be completed into a QFT and those which cannot. Next, we consider the more optimistic scenario where that dark sector is connected to the Standard Model via a portal. We propose an explanation to the Galactic Center Excess, a robust gamma-ray signal possibly originating from annihilating dark matter. We consider a CP-violating Higgs portal which allows Majorana fermion dark matter to annihilate to Standard Model final states. Measurements of the electron EDM place stringent constraints on viable parameter space. This builds on a separate analysis of the ACME experiment's constraint on the electron EDM and the implications this has for generic models of BSM physics. Precision measurements are an interesting window into models of new physics. In a similar spirit to the analysis of the EDM results, we also consider the anomalous measurement of the W boson mass from the CDF experiment. We characterize this tension in terms of the oblique parameters, and discuss various models of new physics which can generate the required values to alleviate the tension between the measurement and Standard Model prediction. Finally, we consider a separate portal where the dark sector is endowed with a U(1) and kinetically mixes with the Standard Model U(1). With the expectation that the dark and visible sectors must ultimately embed into a complete theory of quantum gravity, we use the Swampland conjectures to place constraints on the size of the kinetic mixing parameter.

This dissertation consists of five chapters. The first broadly and briefly orients the reader through an introduction to inflationary cosmology, and why we might expect multi-field inflation to take place. The next four chapters correspond to distinct lines of research conducted during my time as a graduate student. Chapter two is based on work conducted with my advisor Sonia Paban, studying the landscape of possible multi-field inflationary models through a random-matrix generated potential [1]. Chapter three is based on work with Diederik Roest and Perseas Christodoulidis, studying universality and prior dependence in multi-field inflation [2]. Chapters four and five are based on work with Sonia Paban and Vikas Aragam, studying inflation in potentials compatible with quantum gravity and rapidly turning trajectories [3, 4].

This dissertation consists of five chapters. The first broadly and briefly orients the reader through an introduction to inflationary cosmology, and why we might expect multi-field inflation to take place. The next four chapters correspond to distinct lines of research conducted during my time as a graduate student. Chapter two is based on work conducted with my advisor Sonia Paban, studying the landscape of possible multi-field inflationary models through a random-matrix generated potential [1]. Chapter three is based on work with Diederik Roest and Perseas Christodoulidis, studying universality and prior dependence in multi-field inflation [2]. Chapters four and five are based on work with Sonia Paban and Vikas Aragam, studying inflation in potentials compatible with quantum gravity and rapidly turning trajectories [3, 4].