Science with a 16 m vlt: The case for variability of fundamental constants

Abstract

Only astronomical observations can effectively probe in space-time the variability of the physical dimensionless constants such as the fine structure constant α and proton-to-electron mass ratio, μ, which are related to fundamental forces of nature. Several theories beyond the Standard Model (SM) allow fundamental constants to vary, but they cannot make quantitative predictions so that only laboratory experiments and astronomical observations can show if this is the case or set the allowed bounds. At the moment of writing there are claims for a variability of both α and μ at 5 and 4 σ of C.L., respectively, although for α they are contrasted by null results. The observations are challenging and a new spectrograph such as ESPRESSO at the combined incoherent focus of 4 VLT units (a potential 16 m equivalent telescope) will allow for a significant improvement in the precision measurement clearing up the controversy. If the variations will be confirmed, the implications are far reaching, revealing new physics beyond the SM and pointing a direction for GUTs theories. A most exciting possibility is that a variation of α is induced by quintessence through its coupling with the electromagnetic field. If this is the case an accurate measurement of the variability could provide a way for reconstructing the equation of state of Dark Energy [P. Avelino, C.J.A.P. Martins, N.J. Nunes, K.A. Olive in Phys. Rev. D 74, 083508 (2006)].