Observing the temperature of the Big Bang through large scale structure

TL;DR

This paper investigates the primordial thermal imprint on the universe's large scale structure, using cosmic microwave background data to constrain early universe temperatures and exploring thermal fluctuation scenarios.

Contribution

It introduces a method to analyze thermal residues in large scale structure and constrains early universe temperatures based on CMB observations.

Findings

Constraints on the temperature of the universe before and during inflation.

Comparison of thermal fluctuations with vacuum fluctuations in large scale structure.

Proposal of an alternative thermal fluctuation scenario near scale-invariance.

Abstract

It is widely accepted that the Universe underwent a period of thermal equilibrium at very early times. One expects a residue of this primordial state to be imprinted on the large scale structure of space time. In this paper we study the morphology of this thermal residue in a universe whose early dynamics is governed by a scalar field. We calculate the amplitude of fluctuations on large scales and compare it to the imprint of vacuum fluctuations. We then use the observed power spectrum of fluctuations on the cosmic microwave background to place a constraint on the temperature of the Universe before and during inflation. We also present an alternative scenario where the fluctuations are predominantly thermal and near scale-invariant.