Varying fundamental constants?: Observational status and future prospects

Michael Murphy
Swinburne University of Technology

Variations in the fundamental constants would directly violate the
Standard Model of particle physics and Einstein's equivalence
principle. Some modern unified theories actually predict variations in
the (low-energy) values of the constants, linking them to changes in
the typical sizes of extra, compactified dimensions of space. Many
dedicated laboratory and satellite experiments currently test for
variations over human timescales but it is essential to probe a much
larger range of times and distances. Remarkably, absorption systems
along the sight-lines to distant quasars offer our most precise
extragalactic probe of variations in the fine-structure constant and
the proton-to-electron mass ratio. I will discuss the current evidence
for and against variations in both these fundamental parameters. I
will also describe the potential of newly proposed spectrographs on
current and future telescopes for constraining fundamental physics at
high redshifts at a precision competitive with advances in laboratory
experiments. Calibrating these spectrographs poses a particular
challenge and I will outline our proposal for doing so with new laser
frequency comb technology.