Black hole complementarity and string theory

Herein is presented an investigation of the black hole information paradox. The conjecture of black hole complementarity, and its possible realization in string theory, provide a resolution of the paradox.; Three postulates asserting the validity of quantum theory, semi-classical general relativity and statistical mechanics are introduced for the study of black hole evolution. These postulates are implemented with a "stretched horizon" or membrane description of the black hole, appropriate for a distant observer. The analysis is illustrated using two-dimensional dilaton gravity. Our postulates imply the dissipative properties of the stretched horizon arise from a coarse graining of microphysical degrees of freedom.; The entropy of an extremely massive Schwarzschild black hole is studied ill canonical quantum gravity and string theory. The entropy per unit area of a free scalar field is quadratically divergent near the horizon. It is shown that such quantum corrections to the entropy per unit area are equivalent to the quantum corrections to the gravitational coupling. Unlike field theory, string theory provides a set of identifiable configurations which account for the classical contribution to the entropy per unit area, and provide a possible microscopic description of the degrees of freedom of the stretched horizon. The entropy per-unit area is shown to be finite to all orders in string perturbation theory.; The evaporation of a large mass black hole can be described throughout most of its lifetime by a low-energy effective theory defined on a set of smooth spacelike hypersurfaces. The argument for information loss rests on the assumption that the effective theory is local. We present evidence that this assumption fails in the context of string theory. It is shown that the commutator of operators in light-front string field theory, corresponding to low-energy observers on opposite sides of the event horizon, is non-vanishing. This suggests that degrees of freedom inside a black hole should not be viewed as independent from those outside. These nonlocal effects are only significant under extreme kinematic circumstances, such as in the high-redshift geometry of a black hole, and are suppressed in situations corresponding to ordinary low-energy observers in Minkowski space.