Speaker
Description
Recent Dark Energy Spectroscopic Instrument (DESI) results have garnered attention from the cosmology community due to tension with the $\Lambda$CDM cosmological model when combined with cosmic microwave background (CMB) data. The tension suggests that a new model for dark energy may be warranted. Current alternative models focus mainly on a time-varying component of dark energy due in part to ease of computation from maintaining a homogeneous and isotropic universe. We present the consequences of an inhomogeneous dark energy toy model in the form of a first order phase transition of dark energy, i.e., a bubble of reduced dark energy density. We find that the model predictions of Alcock–Paczynski distortion have features that align strikingly well with the DESI measurements if the dark energy phase transition occurred at roughly a redshift of 1.4, and if the bubble of lower dark energy density has roughly 6\% less dark energy density than the outer cosmology. Despite this striking resemblance, we find that the dark energy bubble is heavily constrained by the CMB to the extent that bubbles in the 1$\sigma$ allowed region of the parameter space would be undetectable in any of the DESI redshift bins, rendering the bubble cosmology indistinguishable from $\Lambda$CDM. Still, the peculiar features in the distance measurements of the dark energy bubble cosmology serve as a suggestive toy model to motivate and inform future work in the currently poorly explored area of spatially varying dynamical dark energy.