We propose a picture, within the pre-big-bang approach, in which the universe emerges from a bath of plane gravitational and dilatonic waves. The waves interact gravitationally breaking the exact plane symmetry and lead generically to gravitational collapse resulting in a singularity with the Kasner-like structure. The analytic relations between the Kasner exponents and the initial data are exp...

This paper presents the complete algorithm of site response analysis of nonhomogeneous topographic structures using transient two-dimensional boundary element method (BEM). Seismic behaviour of various topographic features including canyon, half plane, sedimentary filled valley and ridge sections, subjected to incident SV and P waves are analysed. The analysis shows the efficiency of the propos...

In this note we aim to study plane-wave limits of the solutions of type II superstring theories. We consider Freund-Rubin type dS5 ×H5 solutions of type IIB theory and obtain a new kind of plane-wave solutions, we refer them as de Sitter plane-waves or Dpp-waves. Considering Hull’s time-like T-duality we are able to map the Dpp wave solution to maximally supersymmetric Hpp-wave in IIB string th...