Black holes and self-interacting fundamental strings

by Diego Chialva (Nordita)

Monday 27 Apr 2009, 13:15 → 14:15 Europe/Stockholm

122:026

Black holes are classical objects having properties that require an explanation in the setup of quantum theory. Research has commonly concentrated on the entropy, interpreting black holes' one as the counting of some microstates. The right microstates to count upon must of course have the correct quantum numbers (mass, charges, angular momentum) to match those of the black hole, but must also possess some geometrical properties (size) due to the particularity of the black hole metric (presence of an horizon). Nowadays, a leading candidate for a quantum gravity theory is string theory. Two problems arise in trying to obtain the black hole entropy from strings: on one side the geometrical requirements on the microstates complicates the counting very much, because it is difficult in the microscopical theory to implement them. On the other side, the black hole and string entropies are usually computed in different regimes (free versus interacting theory) and therefore for non-BPS configurations the interactions of the string should be taken into account to match the results. The string/black holes correspondence principle allows us to compare the two entropies computed in the perturbative regime, but this requires computing one-loop corrections to the tree-level counting, which is notoriously difficult in string theory. In this talk we present a solution both to the problem of investigating the geometrical properties of the string microstates and of taking into account their interactions. We consider configurations with and without (Neveu-Schwarz) charges and show how geometrical quantities, such as typical string sizes equal to the radius of the corresponding black holes, arise in the description of string states at non-zero coupling.