IA/U.Lisboa Seminar - Absorption of scalars by black holes in string theory - 09 abril 2018

We analyze the low frequency absorption cross section of minimally coupled massless scalar fields by different kinds of nonextremal black holes in string theory. In each case we show that this cross section always has the form of some parameter of the solution divided by the black hole Hawking temperature. We also verify in each case that, despite its explicit temperature dependence, such quotient is finite in the extremal limit, yielding a well defined cross section. We show that such cross section for extremal black holes in d dimensions is equal to the horizon area, even in the presence of string-theoretical corrections. Classically one has the relation sigma=4GS between that cross section and the black hole entropy; we discuss the validity of such relation in the presence of higher derivative corrections for extremal black holes in many different contexts.