Vacuum quantum effect for curved boundaries in static Robertson--Walker spacetime

The energy-momentum tensor for a massless conformally coupled scalar field in the region between two curved boundaries in $k=-1$ static Robertson--Walker spacetime is investigated. We assume that the scalar field satisfies the Dirichlet boundary condition on the boundaries. $k=-1$ Robertson--Walker space is conformally related to the Rindler space, as a result we can obtain vacuum expectation values of energy-momentum tensor for conformally invariant field in Robertson--Walker space from the corresponding Rindler counterpart by the conformal transformation.Comment: 7 pages, no figures; Clarifying comments added, no physics changed, version to appear in PLB (2009

Gamma Modules

Let R be a Γ-ring. We introduce the notion of gamma modules over R and study important properties of such modules. In this regards we study submodules and homomorphism of gamma modules and give related basic results of gamma modules