Stasis, Stasis, Triple Stasis

TL;DR

This paper explores various forms of cosmological stasis involving matter, radiation, and vacuum energy, revealing their universality and potential inevitability in beyond Standard Model (BSM) cosmologies, and introduces a formalism to understand their emergence.

Contribution

It extends previous work on matter/radiation stasis to include vacuum energy and introduces the concept of triple stasis, providing a general formalism for their emergence in BSM cosmologies.

Findings

Universal attractors for stasis epochs in cosmology.

Existence of triple stasis with fixed matter, radiation, and vacuum energy.

Introduction of quasi-stasis and oscillatory stasis variants.

Abstract

Many theories of BSM physics predict the existence of large or infinite towers of decaying states. In a previous paper (arXiv:2111.04753) we pointed out that this can give rise to a surprising cosmological phenomenon that we dubbed "stasis" during which the relative abundances of matter and radiation remain constant across extended cosmological eras even though the universe is expanding. Indeed, such stasis epochs are universal attractors, with the universe necessarily entering (and later exiting) such epochs for a wide variety of initial conditions. Matter/radiation stasis is therefore an important and potentially unavoidable feature of many BSM cosmologies. In this paper we extend our arguments to universes containing significant amounts of vacuum energy, and demonstrate that such universes also give rise to various forms of stasis between vacuum energy and either matter or radiation. We also demonstrate the existence of several forms of "triple stasis" during which the abundances of matter, radiation, and vacuum energy all simultaneously remain fixed despite cosmological expansion. We further describe several close variants of stasis which we call "quasi-stasis" and "oscillatory stasis" and discuss the circumstances under which each of these can arise. Finally, we develop a general formalism for understanding the emergence of stasis within BSM cosmologies irrespective of the number or type of different energy components involved. Taken together, these results greatly expand the range of theoretical and phenomenological possibilities for the physics of the early universe, introducing new types of cosmological eras which may play an intrinsic and potentially inevitable role within numerous BSM cosmologies.