Does the generalized second law require entropy bounds for a charged system? art. no. 064020

We calculate the net change in generalized entropy occurring when one carri es out the gedanken experiment in which a box initially containing energy E , entropy S and charge Q is lowered adiabatically toward a Reissner-Nordstr om black hole and then its contents are released into the black hole. Origi nally, it had been thought that this process with Q = 0 might violate the g eneralized second law of thermodynamics. However, Unruh and Wald showed tha t the effects of acceleration radiation prevent violation of the generalize d second law. In our more generic case with the charged contents of the box , we show that the properties of the thermal atmosphere play an equally imp ortant role as a neutral box case. Indeed, we prove here that an equilibriu m condition for the thermal atmosphere and the physical properties of ordin ary matter are sufficient to enforce the generalized second law. Thus, no a dditional assumptions concerning the entropy bounds on the contents of the box need to be made in this process. The relation between our results and t he recent work by Bekenstein and Mayo [Phys. Rev. D 61, 024022 (2000)], and Hod [gr-qc/9903010; Phys. Rev. D 61, 024023 (2000)] on entropy bounds for charged systems are also discussed.