# Talk:Bekenstein bound

## Reviewer B

I think this is a very nice introduction to the Bekenstein bound. I also agree with the author that all early objections to the derivation of the bound from the generalized second law were eventually responded satisfactorily. However, there is one important point raised in (D. Marolf, D. Minic, S. F. Ross, Phys. Rev. D69, 064006 (2004), D. Marolf, arXiv:hep-th/0410168) which could also be addressed by the article, and which may lead to substantial modifications to the content of the bound. The essential point made by these authors is that in the region exterior to the black hole one should count also the entropy of the thermal atmosphere, which is present before and after the object falls down to the black hole. Taking into account these entropies could make the bound to hold regardless of the object matter content. This point is related with the fact that the quantities involved in the bound, energy and entropy, are ill defined for a localized state in a relativistic theory. This is due to particle pair production induced by the localization. In order to properly define the bound the entropy and energy of this cloud of created particles should be taken into account (see for example my article in Class. Quant. Grav. 25, 205021 (2008), arXiv:0804.2182).

H. Casini

## Reviewer A

In the article Bekenstein bound' the problem of many species' has been somewhat paramount. even though it is covered in the reference given (Bekenstein 2005) at the end, it seems to me more fundamental than the other objections that he addresses in that paper. perhaps a comment on this could be included in the article (i think this problem might make te Bekenstein bound somewhat different in principle from the holographic bound, for instance)