Matter Bounce in Horava-Lifshitz Cosmology

TL;DR

This paper explores how Horava-Lifshitz gravity can produce a matter bounce cosmology, offering an alternative to inflation that naturally generates a scale-invariant spectrum of primordial fluctuations.

Contribution

It demonstrates that Horava-Lifshitz cosmology can realize the matter bounce scenario, preserving scale-invariance of fluctuations through the bounce and predicting distinctive bispectrum signatures.

Findings

Scale-invariant spectrum of curvature perturbations is preserved during the bounce.

Quantum vacuum fluctuations exit the Hubble radius and become scale-invariant on super-Hubble scales.

Distinctive bispectrum predictions arise from the matter bounce scenario.

Abstract

Horava-Lifshitz gravity, a recent proposal for a UV-complete renormalizable gravity theory, may lead to a bouncing cosmology. In this note we argue that Horava-Lifshitz cosmology may yield a concrete realization of the matter bounce scenario, and thus give rise to an alternative to inflation for producing a scale-invariant spectrum of cosmological perturbations. In this scenario, quantum vacuum fluctuations exit the Hubble radius in the pre-bounce phase and the spectrum is transformed into a scale-invariant one on super-Hubble scales before the bounce because the long wavelength modes undergo squeezing of their wave-functions for a longer period of time than shorter wavelength modes. The scale-invariance of the spectrum of curvature fluctuations is preserved during and after the bounce. A distinctive prediction of this scenario is the amplitude and shape of the bispectrum.