Out of equilibrium: understanding cosmological evolution to lower-entropy states

TL;DR

This paper explores how large fluctuations out of equilibrium, relevant to cosmology, can spontaneously occur and are related to their relaxation processes, shedding light on the spacetime structure of such events.

Contribution

It introduces a general framework linking the most probable fluctuation paths to their relaxation counterparts, enhancing understanding of cosmological fluctuations in de Sitter and anti-de Sitter spaces.

Findings

Most likely fluctuation history is CPT conjugate of relaxation path

Spacetime structures of fluctuations in de Sitter space elucidated

Analysis of fluctuations in thermal anti-de Sitter space provided

Abstract

Despite the importance of the Second Law of Thermodynamics, it is not absolute. Statistical mechanics implies that, given sufficient time, systems near equilibrium will spontaneously fluctuate into lower-entropy states, locally reversing the thermodynamic arrow of time. We study the time development of such fluctuations, especially the very large fluctuations relevant to cosmology. Under fairly general assumptions, the most likely history of a fluctuation out of equilibrium is simply the CPT conjugate of the most likely way a system relaxes back to equilibrium. We use this idea to elucidate the spacetime structure of various fluctuations in (stable and metastable) de Sitter space and thermal anti-de Sitter space.