Gravity, particle physics and their unification

We explain the need for a theory of quantum gravity and some general ideas about string theory, including the idea of the derivation of the Hawking Bekenstein entropy formula for extremal black holes. We then give a general description of the correspondence between the large N limit of certain gauge theories and string theory on spacetimes with boundaries.Comment: latex, 8 figures. Talk at Lepton-Photon 99. Talk for non-string-theorist

Exact results for the entanglement entropy and the energy radiated by a quark

We consider a spherical region with a heavy quark in the middle. We compute the extra entanglement entropy due to the presence of a heavy quark both in ${\cal N}=4$ Super Yang Mills and in the ${\cal N}=6$ Chern-Simons matter theory (ABJM). This is done by relating the computation to the expectation value of a circular Wilson loop and a stress tensor insertion. We also give an exact expression for the Bremsstrahlung function that determines the energy radiated by a quark in the ABJM theory.Comment: 23+12 pages, 8 figures. V2: references added. V3: references added. V4: small comments and references adde