No-Bang Quantum State of the Cosmos

TL;DR

This paper proposes a quantum state model for the entire universe, combining de Sitter states to explain cosmological entropy and inflation, with implications for understanding the universe's initial conditions.

Contribution

It introduces a novel mixed quantum state of the cosmos based on asymptotic de Sitter states, excluding big bang or crunch scenarios, and explores its entropy and inflation implications.

Findings

Entropy of the state is about three-fourths of de Sitter entropy.

Most component states do not undergo rapid inflation.

Inflation-dominant states may align with observational data.

Abstract

A quantum state of the entire cosmos (universe or multiverse) is proposed which is the equal mixture of the Giddings-Marolf states that are asymptotically single de Sitter spacetimes in both past and future and are regular on the throat or neck of minimal three-volume. That is, states are excluded that have a big bang or big crunch or which split into multiple asymptotic de Sitter spacetimes. (For simplicity, transitions between different values of the cosmological constant are assumed not to occur, though different positive values are allowed.) The entropy of this mixed state appears to be of the order of the three-fourths power of the Bekenstein-Hawking A/4 entropy of de Sitter spacetime. Most of the component pure states do not have rapid inflation, but when an inflaton is present and the states are weighted by the volume at the end of inflation, a much smaller number of states may dominate and give a large amount of inflation and hence may agree with observations.