Eur. Phys. J. C (2016) 76: 130
https://doi.org/10.1140/epjc/s10052-016-3971-6

Regular Article - Theoretical Physics

Variable speed of light cosmology, primordial fluctuations and gravitational waves

¹ Perimeter Institute for Theoretical Physics, Waterloo, Ontario, N2L 2Y5, Canada
² Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada

^* e-mail: jmoffat@perimeterinstitute.ca

Received: 18 September 2015
Accepted: 24 February 2016
Published online: 9 March 2016

Abstract

A variable speed of light (VSL) cosmology is described in which the causal mechanism of generating primordial perturbations is achieved by varying the speed of light in a primordial epoch. This yields an alternative to inflation for explaining the formation of the cosmic microwave background (CMB) and the large scale structure (LSS) of the universe. The initial value horizon and flatness problems in cosmology are solved. The model predicts primordial scalar and tensor fluctuation spectral indices and , respectively. We make use of the formalism to identify signatures of primordial nonlinear fluctuations, and this allows the VSL model to be distinguished from inflationary models. In particular, we find that the parameter in the variable speed of light cosmology. The value of the parameter evolves during the primordial era and shows a running behavior.