Nuclear, Particle, Astroparticle and Cosmology (NUPAC) Seminars
Candidacy Exam: Variation of Fundamental Constants, the Dark Sector, and H_0 (NOTE SPECIAL TIME)
Presented by Kylar Greene, UNM
The Hubble-Lemaitre tension has created an exciting realm within cosmology to search for new physics. Changes to both early-time and late-time cosmology have been proposed in many forms, with varying degrees of success due to a focus on the singular summary statistic, H_0. Here we demonstrate that late-time solutions do not necessarily address the measurements in tension -- the distances -- and could lead to spurious detection of new physics. Therefore, we focus on early-Universe solutions utilizing a previously overlooked symmetry of cosmological observables. The transformation adjusts all of the relevant time and length scales which allows any rate in the early-Universe to be changed, including H(z). A possible realization is to include a new mirror world dark sector which increases the energy density. However, the photon scattering rate must also be changed while keeping the cosmic microwave background observables constant. By varying the electromagnetic fine structure constant and the electron mass we show that we can change the photon scattering rate without changing the timing of recombination. However, there is much work to do in resolving issues with big bang nucleosynthesis, the possible mechanisms behind the proposed variation of fundamental constants, and exploring the parametric freedom of the dark sector.
3:00 pm, Thursday, January 20, 2022
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