On the "scattering law" for Kasner parameters appearing in asymptotics of an exact S-brane solution

Abstract

A multidimensional cosmological model with scalar and form fields [1-4] is studied. An exact S-brane solution (either electric or magnetic) in a model with l scalar fields and one antisymmetric form of rank m > 1 is considered. This solution is defined on a product manifold containing n Ricci-flat factor spaces M_1, ..., M_n. In the case when the kinetic term for scalar fields is positive definite we singled out a special solution governed by the function cosh. It is shown that this special solution has Kasner-like asymptotics in the limits \tau \to + 0 and \tau \to + \infty, where \tau is a synchronous time variable. A relation between two sets of Kasner parameters \alpha_{\infty} and \alpha_0 is found. This relation, named as ``scattering law'' (SL) formula, is coinciding with the ``collision law'' (CL) formula obtained previously in [5] in a context of a billiard description of S-brane solutions near the singularity. A geometric sense of SL formula is clarified: it is shown that SL transformation is a map of a ``shadow'' part of the Kasner sphere S^{N-2} (N = n+l) onto ``illuminated'' part. This map is just a (generalized) inversion with respect to a point v located outside the Kasner sphere S^{N-2}. The shadow and illuminated parts of the Kasner sphere are defined with respect to a point-like source of light located at v. Explicit formulae for SL transformations corresponding to SM2- and SM5-brane solutions in 11-dimensional supergravity are presented.