String Gas Cosmology and Structure Formation

TL;DR

String gas cosmology's Hagedorn phase can generate nearly scale-invariant scalar fluctuations and predicts a slight blue tilt in gravitational wave spectrum, offering an alternative to inflation-based models.

Contribution

This paper provides detailed computations supporting the mechanism of structure formation in string gas cosmology without requiring inflation.

Findings

Scalar metric fluctuations are nearly scale-invariant.

Gravitational wave spectrum exhibits a slight blue tilt.

Supports string gas cosmology as a viable alternative to inflation.

Abstract

It has recently been shown that a Hagedorn phase of string gas cosmology may provide a causal mechanism for generating a nearly scale-invariant spectrum of scalar metric fluctuations, without the need for an intervening period of de Sitter expansion. A distinctive signature of this structure formation scenario would be a slight blue tilt of the spectrum of gravitational waves. In this paper we give more details of the computations leading to these results.