String theory, cosmology and varying constants

Abstract

In string theory the coupling ``constants'' appearing in the low-energy effective Lagrangian are determined by the vacuum expectation values of some (a priori) massless scalar fields (dilaton, moduli). This naturally leads one to expect a correlated variation of all the coupling constants, and an associated violation of the equivalence principle. We review some string-inspired theoretical models which incorporate such a spacetime variation of coupling constants while remaining naturally compatible both with phenomenological constraints coming from geochemical data (Oklo; Rhenium decay) and with present equivalence principle tests. Barring a very unnatural fine-tuning of parameters, a variation of the fine-structure constant as large as that recently ``observed'' by Webb et al. in quasar absorption spectra appears to be incompatible with these phenomenological constraints. Independently of any model, it is emphasized that the best experimental probe of varying constants are high-precision tests of the universality of free fall, such as MICROSCOPE and STEP.

13 pages, invited talk at the JENAM 2002 workshop on Varying Fundamental Constants

References in corpus (7)

• Quintessence as a run-away dilaton
• Violations of the equivalence principle in a dilaton-runaway scenario
• Runaway dilaton and equivalence principle violations
• A Simple Varying-alpha Cosmology
• Evolution of the Fine Structure Constant Driven by Dark Matter and the Cosmological Constant
• Constraints on the Variations of the Fundamental Couplings
• Large-N bounds on, and compositeness limit of, gauge and gravitational interactions

Cited by in corpus (16)

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• Reconstructing the dark energy equation of state with varying couplings
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• How fundamental are fundamental constants?
• The variation of the gravitational constant inferred from the Hubble diagram of Type Ia supernovae
• Fundamental cosmology in the E-ELT era: The status and future role of tests of fundamental coupling stability
• Possible variations of the fine structure constant $\alpha$ and their metrological significance
• Lensing amplitude anomaly and varying electron mass alleviate the Hubble and $S_8$ tensions
• Contributions from Dilatonic Strings to the Flat Behaviour of the Rotational Curves in Galaxies
• The variation of G in a negatively curved space-time
• Astrophysical Probes of Fundamental Physics
• Degravitation and the relaxed Einstein equations