Charge conservation and time-varying speed of light

Abstract

It has been recently claimed that cosmologies with time dependent speed of light might solve some of the problems of the standard cosmological scenario, as well as inflationary scenarios. In this letter we show that most of these models, when analyzed in a consistent way, lead to large violations of charge conservation. Thus, they are severly constrained by experiment, including those where c is a power of the scale factor and those whose source term is the trace of the energy-momentum tensor. In addition, early Universe scenarios with a sudden change of c related to baryogenesis are discarded.Since one of the key hypothesis of special relativity is the frame independence of the velocity of light c, it is implied in this statement the time and space independence of this velocity. As well established that it may seem, this constancy principle has been recently contested [1,2] to provide an alternative account of the horizon, flatness and cosmological constant problems present in the standard big bang scenario. Instead of the superluminal expansion of the Universe present in inflationary scenarios, a period in which light traveled much faster than today would explain the homogeneity we see today in the Universe. Some cosmological models have also been analyzed afterwards [3,4] to test the dynamical viability of this scenario.These ideas are highly provocative, not only from the observational viewpoint but also from the conceptual one. Indeed one of the key aspects of Einstein equivalence principle is the time-independence of the so called "fundamental constants" of physics [5]. The replacement of these parameters by one or more dynamical fields can lead to time-as well as space-dependent local fundamental constants. Unification schemes such as superstring theories [6] and Kaluza-Klein theories [7] have cosmological solutions in which the low-energy fundamental constants are functions of time. Usually low-energy phenomena are * Fellow of FOMEC † Member of CONICET 1

A scalar-tensor cosmological model with dynamical light velocity

“…Therefore the matter model lives on a geometry described by a metricĝ µν , and we do not expect that our model will be in conflict with any direct equivalence principle tests, nor will it violate charge conservation in the manner described in [33]. The strong equivalence principle is violated, and it is the gravitational reaction to the presence of matter that is altered.…”

Behavior of varying-alpha cosmologies

“…This is done by letting e take on the value of a real scalar field which varies in space and time (for more complicated cases, resorting to complex fields undergoing spontaneous symmetry breaking, see the case of fast tracks discussed in [7]). Thus e 0 → e = e 0 ǫ(x µ ), where ǫ is a dimensionless scalar field and e 0 is a constant denoting the present value of e. This operation implies that some well established assumptions, like charge conservation, must give way [23]. Nevertheless, the principles of local gauge invariance and causality are maintained, as is the scale invariance of the ǫ field (under a suitable choice of dynamics).…”

Untitled

“…This is done by letting e take on the value of a real scalar field which varies in space and time (for more complicated cases, resorting to complex fields undergoing spontaneous symmetry breaking, see the case of fast tracks discussed in [32]). Thus e 0 → e = e 0 ǫ(x µ ), where ǫ is a dimensionless scalar field and e 0 is a constant denoting the present value of e. This operation implies that some well established assumptions, like charge conservation, must give way [33]. Nevertheless, the principles of local gauge invariance and causality are maintained, as is the scale invariance of the ǫ field (under a suitable choice of dynamics).…”