Second Law of Black Hole Mechanics for all 2d Dilaton Theories
arXiv:hep-th/0009145 · doi:10.1103/PhysRevD.63.024021
Abstract
It is shown that all generalized two--dimensional dilaton theories with arbitrary matter content (with a curvature independent coupling to gravity) do not only obey a first law of black hole mechanics (which follows from Wald's general considerations, if the entropy S is defined appropriately), but also a second law: δS \ge 0 provided only that the null energy condition holds and that, loosely speaking, for late times a stationary state is assumed. Also any two-dimensional f(R)--theory is covered. This generalizes a previous proof of Frolov [1] to a much wider class of theories.
12 pages, no figures, References added, one formula (without change of the results) corrected