How to Reconstruct a Varying Speed of Light Signal from Baryon Acoustic Oscillations Surveys

Vincenzo Salzano

doi:10.3390/universe3020035

Abstract

We describe an alternative way to use future Baryon Acoustic Oscillation observations to perform non-mainstream research. We focus on the so-called Varying Speed of Light theories, in which the speed of light is made to vary in time. Using prescriptions from future BAO surveys (BOSS, DESI, WFirst-2.4 and SKA), we show that, within such surveys, a 1% Varying Speed of Light (VSL) signal could be detected at 3 sigmas confidence level, in the redshift interval [0.75, 1.45]. Smaller signals will be hardly detected. We also discuss some possible problems related to such kinds of observation, in particular, the degeneracy between a VSL signal and a non-null spatial curvature.

Highlights

Within the topic “variation of fundamental constants”, the Varying Speed of Light (VSL) theories have a peculiar position, due to a quite vivid debate about their soundness and usefulness [1,2,3].Most of the concerns are related to what can be summarized as the “dimensional vs dimensionless”question: the speed of light c0 1 is a dimensional quantity and, as such, any investigation about its variation should be misleading and not well-based, because one can always define a unique set of units of length and time for which c0 is constant
Having in mind such preliminaries, in [8,9] we have found that a constant speed of light or a more general VSL theory can be intimately related to a dimensionless parameter which is strictly equal to 1, if the speed of light is constant, and different from 1, if it is varying
In [8,9], we have explored the possibility to measure the speed of light at only the maximum redshift z M through this parameter; here, we will show how to use Baryon Acoustic Oscillations (BAO) surveys to measure a possible VSL signal on an extended redshift range

Summary

Introduction

Within the topic “variation of fundamental constants”, the Varying Speed of Light (VSL) theories have a peculiar position, due to a quite vivid debate about their soundness and usefulness [1,2,3]. It is worth noting that many of such concerns might be alleviated if the speed of light were properly introduced after the Lagrangian definition as a scalar field; this is done in [6], but it is not completely solved, because c appears in the line element and whenever the time coordinate happens to be (with consequences, as described in [7]) Having in mind such preliminaries, in [8,9] we have found that a constant speed of light or a more general VSL theory can be intimately related to a dimensionless parameter which is strictly equal to 1, if the speed of light is constant, and different from 1, if it is varying. In [8,9], we have explored the possibility to measure the speed of light at only the maximum redshift z M through this parameter; here, we will show how to use BAO surveys to measure a possible VSL signal on an extended redshift range

Build Up the Method

Results and Conclusions