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Zusammenfassung:
We present a class of numerical solutions to the SU(2) nonlinear sigma model coupled to the Einstein equations with a cosmological constant Lambda>=0 in spherical symmetry. These solutions are characterized by the presence of a regular static region which includes a center of symmetry. They are parametrized by a dimensionless "coupling constant" beta, the sign of the cosmological constant, and an integer "excitation number" n. The phenomenology we find is compared to the corresponding solutions found for the Einstein-Yang-Mills (EYM) equations with a positive Lambda (EYMLambda). If we choose Lambda positive and fix n, we find a family of static spacetimes with a Killing horizon for 0<=beta<betamax. As a limiting solution for beta= betamax we find a globally static spacetime with Lambda= 0, the lowest excitation being the Einstein static universe. To interpret the physical significance of the Killing horizon in the cosmological context, we apply the concept of a trapping horizon as formulated by Hayward. For small values of beta an asymptotically de Sitter dynamic region contains the static region within a Killing horizon of cosmological type. For strong coupling the static region contains an "eternal cosmological black hole."
