Stasis in an Expanding Universe: A Recipe for Stable Mixed-Component Cosmological Eras

May 24, 2022, 11:36 AM


Fei Huang (ITP CAS and UC Irvine)


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 talk, 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 $\Omega_i$ 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 towards 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.

Primary author

Fei Huang (ITP CAS and UC Irvine)


Brooks Thomas Keith Dienes (University of Arizona) Tim M.P. Tait (University of California, Irvine) Doojin Kim (Texas A & M University (US)) Lucien Heurtier (IPPP, Durham, England)

Presentation materials