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

Abstract

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 ${\Omega }_i$ 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.

28 pages, LaTeX, 8 figures

References in corpus (15)

• Dynamics of dark energy
• Neutralino with the Right Cold Dark Matter Abundance in (Almost) Any Supersymmetric Model
• The First Three Seconds: a Review of Possible Expansion Histories of the Early Universe
• The effect of a late decaying scalar on the neutralino relic density
• Phase Transitions in an Expanding Universe: Stochastic Gravitational Waves in Standard and Non-Standard Histories
• Thermal Dark Matter From A Highly Decoupled Sector
• Towards a Non-Supersymmetric String Phenomenology
• Non-thermal Histories and Implications for Structure Formation
• Primordial Black Hole Evaporation and Dark Matter Production: II. Interplay with the Freeze-In/Out Mechanism
• Dynamical Dark Matter from Strongly-Coupled Dark Sectors
• Superheavy Thermal Dark Matter and Primordial Asymmetries
• Breaking a dark degeneracy: The gamma-ray signature of early matter domination
• Holographic Mixing Quantified
• Non-thermal Dark Matter from Modified Early Matter Domination
• Extracting Dark-Matter Velocities from Halo Masses: A Reconstruction Conjecture

Cited by in corpus (10)

• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• Primordial black holes from single-field inflation: a fine-tuning audit
• Evaporation of Primordial Black Holes in the Early Universe: Mass and Spin Distributions
• Primordial Black Hole Archaeology with Gravitational Waves from Cosmic Strings
• Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies
• On the Generality and Persistence of Cosmological Stasis
• Constraints on the maximal number of dark degrees of freedom from black hole evaporation, cosmic rays, colliders, and supernovae
• NSC++: Non-Standard Cosmologies in C++
• Cosmological Stasis from Field-Dependent Decay
• The Forward Physics Facility at the High-Luminosity LHC