2003/05/31 by João Magueijo, Joao Magueijo · 8 citations
Physics and Astronomy · #CMB cold spot #Cosmic background radiation #Cosmology #Cosmology and Gravitation Theories #Dark energy #Gamma-ray burst #General relativity #Lorentz covariance #Noncommutative and Quantum Gravity Theories #Observational cosmology #Redshift #Relativity and Gravitational Theory #Speed of light (cellular automaton) #astro-ph #gr-qc #hep-ph #hep-th
paper · pdf · doi:10.1088/0034-4885/66/11/r04
published as Rept.Prog.Phys.66:2025,2003 · Final version
openalex publication_date 2003/10/14 · arxiv created 2003/10/15 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We review recent work on the possibility of a varying speed of light (VSL). We start by discussing the physical meaning of a varying- c , dispelling the myth that the constancy of c is a matter of logical consistency. We then summarize the main VSL mechanisms proposed so far: hard breaking of Lorentz invariance; bimetric theories (where the speeds of gravity and light are not the same); locally Lorentz invariant VSL theories; theories exhibiting a colour-dependent speed of light; varying- c induced by extra dimensions (e.g. in the brane-world scenario); and field theories where VSL results from vacuum polarization or CPT violation. We show how VSL scenarios may solve the cosmological problems usually tackled by inflation, and also how they may produce a scale-invariant spectrum of Gaussian fluctuations, capable of explaining the WMAP data. We then review the connection between VSL and theories of quantum gravity, showing how ‘doubly special’ relativity has emerged as a VSL effective model of quantum space–time, with observational implications for ultra-high energy cosmic rays (UHECRs) and gamma ray bursts. Some recent work on the physics of ‘black’ holes and other compact objects in VSL theories is also described, highlighting phenomena associated with spatial (as opposed to temporal) variations in c . Finally, we describe the observational status of the theory. The evidence is currently slim—redshift dependence in the atomic fine structure, anomalies with UHECRs, and (to a much lesser extent) the acceleration of the universe and the WMAP data. The constraints (e.g. those arising from nucleosynthesis or geological bounds) are tight but not insurmountable. We conclude with the observational predictions of the theory and the prospects for its refutation or vindication.