Heterotic Coset Models of Microscopic Strings and Black Holes

Following a recent conjecture by Lapan, Simons and Strominger, we revisit and discuss an intrinsically heterotic class of conformal field theories, emphasizing their Lagrangian construction as asymmetrically gauged WZW models, which may be useful in several applications to the study of supersymmetric strings and black holes in heterotic and type II string theory compactified on T 6 and K3 × T 2 respectively. In these cases, the leading supergravity geometry is singular, but higher order corrections remove this singularity in a way that is consistent with, for example the non–zero entropy for the black holes. The conformal field theories have exactly the right structure to capture the features of the supergravity analysis, and possess precisely the microscopic target spaces required. We focus on two models in particular, one with AdS3×S geometry, which is conjectured by Lapan et. al. to represent a fundamental heterotic string in five dimensions, and another with AdS2 × S2 geometry, which we conjecture is the exact conformal field theory representing a circle–wrapped fundamental heterotic string in four dimensions where it is a microscopic black hole. We also present conformal field theories which are potential candidates for the microscopic geometry of heterotic strings in higher dimensions, emphasizing some aspects of their similarities to and differences from the four and five dimensional cases.