272 research outputs found

    Couplings varying on cosmological scales and Lorentz breaking

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    In the context of N=4 supergravity in four dimensions, we present an exact classical solution that leads to spacetime-dependent electromagnetic couplings and discuss the ensuing Lorentz-violating effects. We comment briefly on experimental bounds.Comment: 10 pages, 1 figure, invited talk presented at the Coral Gables Meeting, December 200

    Cosmology and spacetime symmetries

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    Cosmological models often contain scalar fields, which can acquire global nonzero expectation values that change with the comoving time. Among the possible consequences of these scalar-field backgrounds, an accelerated cosmological expansion, varying couplings, and spacetime-symmetry violations have recently received considerable attention. This talk studies the interplay of these three key signatures of cosmologically varying scalars within a supergravity framework.Comment: 5 pages; Prepared for New Worlds in Astroparticle Physics, Faro, Portugal, January 8-10, 200

    Apparent Lorentz violation through spacetime-varying couplings

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    In this talk, we explore the relation between smoothly varying couplings and Lorentz violation. Within the context of a supergravity model, we present an explicit mechanism that causes the effective fine-structure parameter and the effective electromagnetic θ\theta angle to acquire related spacetime dependences. We argue that this leads to potentially observable Lorentz violation and discuss some implications for the Standard-Model Extension.Comment: 8 pages; Presented at the 4th Meeting on New Worlds in Astroparticle Physic
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