Black Holes: Supersymmetry and the Information Paradox
Abstract
Part I. U(1)otimes U(1) asymptotically flat dilaton black holes are investigated in the context of N = 4, d = 4 supergravity, or dimensionally reduced superstring theory. It is found that extremal (multi) black holes are supersymmetric, and that the supersymmetric positivity bounds on the black hole mass coincide with the bounds coming from cosmic censorship. Temperature, entropy and horizon properties are discussed in connection with the extremal limit. The onshell action is given and for extremal black holes is argued to be unaltered by higherorder quantum corrections in the supersymmetric theory. The entropy is related to the Euclidean action via the GibbonsHawking method, is found to be onequarter of the horizon area, and vanishes for maximally supersymmetric black holes. Lastly, the nearhorizon behavior of extremal black holes is investigated. N = 1 supersymmetric black holes are found to tend to a RobinsonBertottitype geometry with doubling of supersymmetries; no such doubling is found for the N = 2 case. Part II. Topics relevant to the Information Paradox of black hole physics are investigated. First, 't Hooft's Smatrix approach to the puzzles of black hole evaporation is clarified by considering d = 1 + 1 electrodynamics in a linear dilaton background; analogues of black holes, Hawking evaporation, and an information paradox exist in this system. The paradox is resolved in the full quantum theory where the exact Smatrix is calculated. Secondly, a study of tachyon hair on black holes in twodimensional string theory is presented. Such black holes if static can have tachyon hair; configurations nonsingular at the horizon have nonvanishing asymptotic energy density. There also exist static solutions with finite total energy and singular horizon. Dynamical arguments suggest that neither type of tachyon hair will be present on a black hole formed in gravitational collapse. Lastly, thermalization of a (fundamental) string falling toward the horizon of a four dimensional black hole is investigated. It is found that the transverse string spreading can be described as a branching diffusion of wee string bits. This stochastic process thermalizes the quantum state of the string as it spreads across the stretched horizon.
 Publication:

Ph.D. Thesis
 Pub Date:
 January 1994
 Bibcode:
 1994PhDT........18P
 Keywords:

 STRING THEORY;
 COSMIC CENSORSHIP;
 GIBBONSHAWKING METHOD;
 TACHYON HAIR;
 GRAVITATIONAL COLLAPSE;
 Physics: Astronomy and Astrophysics;
 Black Holes (Astronomy);
 Supersymmetry;
 Supergravity;
 Quantum Theory;
 String Theory;
 Gravitational Collapse;
 Asymptotic Properties;
 Entropy;
 Temperature Effects;
 Paradoxes;
 Evaporation;
 Stochastic Processes;
 Matrices (Mathematics);
 Flux Density;
 Astrophysics