Probing the constancy of the speed of light with future galaxy survey: The case of SKA and Euclid

Abstract

In [1] a new method to measure the speed of light through Baryon Acoustic Oscillations (BAO) was introduced. Here, we describe in much more detail the theoretical basis of that method, its implementation, and give some newly updated results about its application to forecast data. In particular, we will show that SKA will be able to detect a 1% variation (if any) in the speed of light at 3σ level. Smaller signals will be hardly detected by already-planned future galaxy surveys, but we give indications about what sensitivity requirements should a survey fulfill in order to be successful.

Cosmology with Varying Constants from a Thermodynamic Viewpoint

“…For example, in [45] it is shown that SKA will be able to detect a 1% variation in the speed of light at 3σ level.…”

“…Recently, new methods [44][45][46] have been introduced to detect the possible variation of speed of light by using future galaxy surveys, such as The Square Kilometer Array (SKA), Euclid, and the Wide-Field Infrared Survey Telescope (WFIRST-2.4). For example, in [45] it is shown that SKA will be able to detect a 1% variation in the speed of light at 3σ level.…”

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

“…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. The most interesting point is that such a parameter can be easily measured because it is strictly connected to the typical correlation length imprinted in the clustering of galaxies and thus is related to the Baryon Acoustic Oscillations (BAO) observations.…”

“…In a BAO survey, this correlation length is seen subtending an angle; as such, we determine an angular diameter distance from it. Starting from its definition (see Equation (1) and [8,9]), the angular diameter distance has a peculiar property: it is small for close objects, tending to zero for redshift z → 0; it grows as it goes further from us (grows with redshift); it reaches a maximum and 1 From now on we will define the value of the speed of light we measure here and now as c 0 .…”

“…Thus, any deviation from such value would point toward a VSL scenario. 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.…”