“Cosmological Stasis: Model Realizations, Observational Signatures, and a Possible Connection to Inflation”

Cosmological stasis is a phenomenon in which the abundances of multiple cosmological energy components --- components such as matter, radiation, or vacuum energy --- remain effectively constant despite the expansion of the universe.  In a related talk on Wed., Sept. 18, Prof. Keith Dienes (University of Arizona) provided an overview of this phenomenon and discussed its theoretical underpinnings.  In this talk, I will examine two particular model realizations of stasis which not only emerge naturally within top-down scenarios for new physics, but also have potentially interesting observational consequences.  The first involves the evaporation of a population of primordial black holes with an extended mass spectrum.  As I shall demonstrate, this realization of stasis has potential implications for inflationary observables, for the stochastic gravitational-wave background, and for the production of dark matter and dark radiation.  The second model realization of stasis I shall examine involves a collection of scalar fields, each of which dynamically transitions from a period of slow roll to a period of rapid oscillation around its potential minimum as the universe expands.  This realization exhibits a number of properties not seen in other realizations of stasis.  Moreover, it can also address the horizon problem and can therefore potentially serve as a novel framework for realizing cosmic inflation.