Superstrings on AdS3 at k=1

Understand

We study superstring theory in three dimensional Anti-de Sitter spacetime with NS-NS flux, focusing on the case where the radius of curvature is equal to the string length.

• This corresponds to the critical level k=1 in the Wess-Zumino-Witten description.
• Previously, it was argued that a transition takes place at this special radius, from a phase dominated by black holes at larger radius to one dominated by long strings at smaller radius.
• We argue that the infinite tower of modes that become massless at k=1 is a signal of this transition.