Strings in AdS3: one-loop partition function and near-extremal BTZ thermodynamics

A bstract We revisit the computation of the string partition function in AdS 3 focussing on the appearance of spacetime (super) symmetries. We show how the asymptotic symmetries of the AdS 3 spacetime, which generate the boundary (super) Virasoro currents, are captured by the one-loop partition sum. We use this to argue that the recent understanding of near-extremal black hole thermodynamics based on the gravitational path integral continues to hold for finite string length. Along the way we clarify some aspects of the AdS 3 /CFT 2 duality and, in particular, deduce which bulk gauge fields lead to boundary currents. We also explain how one can interpolate between supersymmetric and thermal (Atick-Witten) fermion boundary conditions in the target space by suitably tuning rotational chemical potentials in the string partition function.