Time Symmetric Quantum Cosmology and Our Universe

TL;DR

This paper examines the time symmetric quantum cosmology model proposed by Gell-Mann and Hartle, demonstrating that our universe's perturbations do not align with the model's predictions, especially regarding initial conditions at the Big Bang.

Contribution

The study critically tests the time symmetric decoherence functional in quantum cosmology against observational perturbations, challenging its applicability to our universe.

Findings

Small inhomogeneous perturbations are not time symmetric near the Big Bang.

Our universe's initial conditions do not match the low entropy, time symmetric state proposed.

The results suggest limitations of the time symmetric approach in describing our universe.

Abstract

We investigate the time neutral formulation of quantum cosmology of Gell-Mann and Hartle. In particular we study the proposal discussed by them that our Universe corresponds to the time symmetric decoherence functional with initial and final density matrix of low entropy. We show that our Universe does not correspond to this proposal by investigating the behaviour of small inhomogeneous perturbations around a Friedman-Robertson-Walker model. These perturbations cannot be time symmetric if they were small at the Big Bang.