Geodesic Properties and Orbits in 5-dimensional Hypercylindrical Spacetime

We investigate the geodesic motions of a massive particle and light ray in the hyperplane orthogonal to the symmetry axis in the 5-dimensional hypercylindrical spacetime. The class of the solutions depends on one constant a which is the ratio of string mass density and tension. There exist unstable orbits in null geodesic only in some range of a. The innermost stable circular orbits in timelike geodesic also exist only in a certain range of the parameter a. The capture cross section and the deflection angle of light ray are also computed.Comment: 17 pages, 10 figures, 4 tables, minor corrected and reference adde

Domain wall cosmology and multiple accelerations

We classify the cosmological behaviors of the domain wall under junctions between two spacetimes in terms of various parameters: cosmological constants of bulk spacetime, a tension of a domain wall, and mass parameters of the black hole-type metric. Especially, we consider the false-true vacuum type junctions and the domain wall connecting between an inner AdS space and an outer AdS Reissner-Nordstr${\rm \ddot{o}}$m black hole. We find that there exist a solution to the junction equations with an inflation at earlier times and an accelerating expansion at later times.Comment: corrected typos, title and sec.

Dynamics of false vacuum bubbles with nonminimal coupling

We study the dynamics of false vacuum bubbles. A nonminimally coupled scalar field gives rise to the effect of negative tension. The mass of a false vacuum bubble from outside observer's point of view can be positive, zero, or negative. The interior false vacuum has de Sitter geometry, while the exterior true vacuum background can have geometry depending on the vacuum energy. We show that there exist expanding false vacuum bubbles without the initial singularity in the past.Comment: 17 pages, 13 figure