Article

Acceleration of the Universe, String Theory and a Varying Speed of Light

06/2001;
Source: arXiv

ABSTRACT The existence of future horizons in spacetime geometries poses serious problems for string theory and quantum field theories. The observation that the expansion of the universe is accelerating has recently been shown to lead to a crisis for the mathematical formalism of string and M-theories, since the existence of a future horizon for an eternally accelerating universe does not allow the formulation of physical S-matrix observables. Postulating that the speed of light varies in an expanding universe in the future as well as in the past can eliminate future horizons, allowing for a consistent definition of S-matrix observables.

0 Bookmarks
 · 
141 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This is a review of aspects of D-brane applications to particle physics and cosmology. D-branes provide interesting alternatives to standard unification of interactions. Moreover they entail new mechanisms in cosmology that have the potential to explain recent observational data.
    Fortschritte der Physik 01/2004; 52(2‐3):200 - 263. · 0.98 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An accelerating Universe can be accommodated naturally within non-critical string theory, in which scattering is described by a superscattering matrix \$ that does not factorize as a product of $S$- and $S^\dagger$-matrix elements and time evolution is described by a modified Liouville equation characteristic of open quantum-mechanical systems. We describe briefly alternative representations in terms of the stochastic Ito and Fokker-Planck equations. The link between the vacuum energy and the departure from criticality is stressed. We give an explicit example in which non-marginal \$tring couplings cause a departure from criticality, and the corresponding cosmological vacuum energy relaxes to zero \`a la quintessence.
    06/2001;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: D-branes are by now an integral part of our toolbox towards understanding nature. In this review, we will describe recent progress in their use to realize fundamental interactions. The realization of the standard model and relevant physics and problems will be detailed. New ideas on realizing four-dimensional gravity use the brane idea in an important way. Such approaches will be reviewed and compared to the standard paradigm of compactification. Branes can play a pivotal role both in early- and late-universe cosmology mainly via the brane-universe paradigm. Brane realizations of various cosmological ideas (early inflation, sources for dark matter and dark energy, massive gravity, etc)are also reviewed.
    Physics Reports 12/2005; · 22.93 Impact Factor

Full-text (2 Sources)

Download
4 Downloads
Available from
Jul 15, 2014