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Particles and Fields

Eur. Phys. J. C 25, 157-164 (2002)
DOI: 10.1007/s10052-002-0981-3

Cosmological evolution in compactified Horava-Witten theory induced by matter on the branes

U. Ellwanger

Laboratoire de Physique Théorique (Unité Mixte de Recherche - CNRS - UMR 8627) , Université de Paris XI, Bâtiment 210, 91405 Orsay Cedex, France

(Received: 8 April 2002 / Published online: 26 July 2002 )

The combined Einstein equations and scalar equation of motion in the Horava-Witten scenario of the strongly coupled heterotic string compactified on a Calabi-Yau manifold are solved in the presence of additional matter densities on the branes. We take into account the universal Calabi-Yau modulus $\varphi$ with potentials in the 5- d bulk and on the 3-branes, and allow for an arbitrary coupling of the additional matter to $\varphi$ and an arbitrary equation of state. No ad hoc stabilization of the five dimensional radius is assumed. The matter densities are assumed to be small compared to the potential for $\varphi$ on the branes; in this approximation we find solutions in the bulk which are exact in y and t. Depending on the coupling of the matter to $\varphi$ and its equation of state, various solutions for the metric on the branes and in the 5- d bulk are obtained: solutions corresponding to a "rolling radius", and solutions with a static 5- d radius, which reproduce the standard cosmological evolution.

© Società Italiana di Fisica, Springer-Verlag 2002