Cosmological Consequences of Nearly Conformal Dynamics at the TeV scale

TL;DR

This paper explores the cosmological implications of nearly conformal dynamics at the TeV scale, highlighting how a strongly first-order phase transition can explain baryogenesis and dark matter abundance even with low reheating temperatures.

Contribution

It introduces a novel scenario where bubble collisions during a first-order phase transition enable baryogenesis and dark matter production at sub-electroweak reheating temperatures.

Findings

Reheating can occur via bubble collisions at low temperatures.

Baryon asymmetry and dark matter can be generated without high-temperature thermal equilibrium.

Potential gravitational wave signatures from the phase transition.

Abstract

Nearly conformal dynamics at the TeV scale as motivated by the hierarchy problem can be characterized by a stage of significant supercooling at the electroweak epoch. This has important cosmological consequences. In particular, a common assumption about the history of the universe is that the reheating temperature is high, at least high enough to assume that TeV-mass particles were once in thermal equilibrium. However, as we discuss in this paper, this assumption is not well justified in some models of strong dynamics at the TeV scale. We then need to reexamine how to achieve baryogenesis in these theories as well as reconsider how the dark matter abundance is inherited. We argue that baryonic and dark matter abundances can be explained naturally in these setups where reheating takes place by bubble collisions at the end of the strongly first-order phase transition characterizing conformal symmetry breaking, even if the reheating temperature is below the electroweak scale $\sim 100$ GeV. We also discuss inflation as well as gravity wave smoking gun signatures of this class of models.