0 v 1 9 M ar 1 99 5 Stationary Strings and 2 - D Black Holes

A general description of string excitations in stationary spacetimes is developed. If a stationary string passes through the ergosphere of a 4-dimensional black hole, its world-sheet describes a 2-dimensional black (or white) hole with horizon coinciding with the static limit of the 4-dimensional black hole. Mathematical results for 2-dimensional black holes can therefore be applied to physical objects (say) cosmic strings in the vicinity of Kerr black holes. An immediate general result is that the string modes are thermally excited. The string exci-tations are determined by a coupled system of scalar field equations in the world-sheet metric. In the special case of excitations propagating along a stationary string in the equatorial plane of the Kerr-Newman black hole, they reduce to the s-wave scalar field equations in the 4-dimensional Reissner-Nordström black hole. We briefly discuss possible applications of our results to the black hole information puzzle. The interaction of strings and black holes is an interesting subject and many publications appeared recently, which discuss different aspects of this problem. The aim of this paper is to attract the attention to the remarkable fact, that the study of propagation of perturbations along a stationary string located in the gravitational field of a stationary 4-dimensional black hole, is directly related with physics of 2-dimensional black holes. If one neglects