Producing a Scale-Invariant Spectrum of Perturbations in a Hagedorn Phase of String Cosmology

TL;DR

This paper explores how a Hagedorn phase in string gas cosmology can generate a nearly scale-invariant spectrum of cosmological perturbations without requiring inflation, potentially explaining observed cosmic fluctuations.

Contribution

It demonstrates, using string thermodynamics, that a Hagedorn phase can produce scale-invariant perturbations, offering an alternative to inflationary models.

Findings

Possible generation of scale-invariant spectrum during Hagedorn phase

Smooth transition from Hagedorn phase to radiation domination

No need for inflation to produce observed fluctuations

Abstract

We study the generation of cosmological perturbations during the Hagedorn phase of string gas cosmology. Using tools of string thermodynamics we provide indications that it may be possible to obtain a nearly scale-invariant spectrum of cosmological fluctuations on scales which are of cosmological interest today. In our cosmological scenario, the early Hagedorn phase of string gas cosmology goes over smoothly into the radiation-dominated phase of standard cosmology, without having a period of cosmological inflation.