Causality properties of topologically nontrivial space-time models

Abstract

Some problems of the space-time causal structure are discussed using models with traversable wormholes. For this purpose the conditions of traversable wormhole matching with the exterior space-time are considered in detail and a mixed boundary problem for the Einstein equations is formulated and analyzed. The influence of these matching conditions on the space-time properties and causal structure is analyzed. These conditions have a non-dynamical nature and cannot be determined by any physical process. So, the causality violation cannot be a result of dynamical evolution of some initial hypersurface. It is also shown that the same conditions which determine the wormhole joining with the outer space provide the self-consistency of solutions and the absence of paradoxes in the case of causality violation.

7 pages, LaTeX; Talk presented at the International School-Seminar "Problems of Theoretical Cosmology", Ulyanovsk, September 1--7, 1997