Collision of Domain Walls and Creation of Matter in Brane World(VIII Asia-Pacific International Conference on Gravitation and Astrophysics (ICGA8))

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We study collision of two domain walls in five-dimensional (5D) spacetime and creation of matter fields. This may provide the reheating mechanism in cosmological models based on a colliding-brane scenario such as the ekpyrotic (or cyclic) universe. We first analyze the dynamics of colliding domain walls both in 5D Minkowski background spacetime and in asymptotic AdS spacetime including self-gravity. We find that multiple bounces appear at collision. In the case with gravity, we find that a spacelike curvature singularity is formed in the bulk, but it is covered by a horizon. Next we analyze production of particles at collision of two domain walls. For a scalar field, the energy density of created particles is evaluated as p ≈ 20^<-4>_g N_b m^4_Φ where g^^- is a coupling constant of particles to a domain-wall scalar field, N_b is the number of bounces at the collision and m_Φ& is a fundamental mass scale of the domain wall. We also study the behaviour of 5D fermions localized on domain walls, when two walls collide in a 5D Minkowski background spacetime. For k = 0 mode, we find that most fermions are localized on both branes as a whole even after collision. However, how much fermions are localized on which brane depends sensitively on the incident velocity and the coupling constants.
理論物理学刊行会の論文
2008-07-09