The Matter Bounce Alternative to Inflationary Cosmology

TL;DR

This paper reviews the matter bounce cosmology as an alternative to inflation, explaining how a contracting universe can produce observed cosmic structures and discussing observational tests to distinguish it from inflation.

Contribution

It provides a comprehensive overview of the matter bounce scenario, including its theoretical development, evolution of fluctuations, and potential observational signatures.

Findings

Matter bounce can produce a nearly scale-invariant spectrum.

Various models attempt to realize the matter bounce scenario.

Distinct observational signatures can differentiate it from inflation.

Abstract

A bouncing cosmology with an initial matter-dominated phase of contraction during which scales which are currently probed with cosmological observations exit the Hubble radius provides a mechanism alternative to inflation for producing a nearly scale-invariant spectrum of cosmological perturbations. In this review article I first discuss the evolution of cosmological fluctuations in the matter bounce scenario, and then discuss various attempts at realizing such a scenario. Observational signatures which will allow the matter bounce to be distinguished from the inflationary paradigm are also discussed.