Stasis in an expanding universe: A recipe for stable mixed-component cosmological eras

Keith R. Dienes, Lucien Heurtier, Fei Huang, Doojin Kim, Tim M.P. Tait, Brooks Thomas

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


One signature of an expanding universe is the time variation of the cosmological abundances of its different components. For example, a radiation-dominated universe inevitably gives way to a matter-dominated universe, and critical moments such as matter-radiation equality are fleeting. In this paper, we point out that this lore is not always correct and that it is possible to obtain a form of "stasis"in which the relative cosmological abundances ωi of the different components remain unchanged over extended cosmological epochs, even as the universe expands. Moreover, we demonstrate that such situations are not fine-tuned but are actually global attractors within certain cosmological frameworks, with the universe naturally evolving toward such long-lasting periods of stasis for a wide variety of initial conditions. The existence of this kind of stasis therefore gives rise to a host of new theoretical possibilities across the entire cosmological timeline, ranging from potential implications for primordial density perturbations, dark-matter production, and structure formation all the way to early reheating, early matter-dominated eras, and even the age of the Universe.

Original languageEnglish (US)
Article number023530
JournalPhysical Review D
Issue number2
StatePublished - Jan 15 2022

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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