Is it e or is it c? Experimental tests of varying alpha

João Magueijo,John D Barrow,Håvard Bunes Sandvik

doi:10.1016/s0370-2693(02)02928-3

João Magueijo, John D Barrow + Show 1 more

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https://doi.org/10.1016/s0370-2693(02)02928-3

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Abstract

Is the recent evidence for a time-varying fine structure ‘constant’ α to be interpreted as a varying e, c, ℏ, or a combination thereof? We consider the simplest varying electric charge and varying speed of light (VSL) theories and prove that for the same type of dark matter they predict opposite senses of variation in α over cosmological times. We also show that unlike varying e theories, VSL theories do not predict violations of the weak equivalence principle (WEP). Varying e theories which explain astronomical inferences of varying α predict WEP violations only an order of magnitude smaller than existing Eötvös experiment limits but could be decisively tested by STEP. We finally exhibit a set of atomic-clock and related experiments for which all (hyperbolic) varying α theories predict non-null results. They provide independent tests of the recent astronomical evidence.

Highlights

Is the recent evidence for a time-varying fine structure ’constant’ α to be interpreted as a varying e, c, h, or a combination thereof? We consider the simplest varying electric charge and varying speed of light theories (VSL) and prove that for the same type of dark matter they predict opposite senses of variation in α over cosmological times
By introducing an appropriate change of units we can turn VSL into a constant c theory, but the dynamics will look unnecessarily complicated; likewise BSBM can be rephrased as a constant e, varying c theory, with a concomitant increase in complexity
This is why we say that BSBM is a varying e theory while the theory in [15] is a VSL theory: dynamics fixes the choice

Summary

Introduction

Is the recent evidence for a time-varying fine structure ’constant’ α to be interpreted as a varying e, c, h, or a combination thereof? We consider the simplest varying electric charge and varying speed of light theories (VSL) and prove that for the same type of dark matter they predict opposite senses of variation in α over cosmological times. We will show that with standard dark matter VSL predicts an increasing α, as a function of cosmological time. This is a striking difference, but pending the determination of the nature of the dark matter one can use both BSBM and VSL to fit the Webb et al results.

Results

Conclusion