2003/10/31 by Kiyotomo Ichiki, K. Nakamura, Kouji Nakamura · 1 citation
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Noncommutative and Quantum Gravity Theories #astro-ph #gr-qc #hep-th
paper · pdf · doi:10.1103/physrevd.70.064017
published as Phys.Rev. D70 (2004) 064017 · 9 pages, 6 figures, accepted for publication in PRD; this version includes the referee's suggestions and expanded discussion on our numerical scheme
arxiv created 2004/08/15 · openalex publication_date 2004/09/14 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The causal structure of the flat brane universe of RSII type is reinvestigated to clarify the boundary conditions for stochastic gravitational waves. In terms of the Gaussian normal coordinate of the brane, a singularity of the equation for gravitational waves appears in the bulk. We show that this singularity corresponds to the ``seam singularity'' which is a singular subspace on the brane universe. Based upon the causal structure, we discuss the boundary conditions for gravitational waves in the bulk. Introducing a null coordinate, we propose a numerical procedure to solve gravitational waves with appropriate boundary conditions and show some examples of our numerical results. This procedure could be also applied in scalar type perturbations. The problem in the choice of the initial condition for gravitational waves is briefly discussed.