IAS Quantum Aspects of Black Holes Group Meeting

Abstract: I will review the correspondence between highly excited strings and black holes in the presence of angular momentum. At fixed imaginary angular velocity $\nu$, free strings exhibit a Hagedorn instability, explained—as in Atick and Witten—by a thermal-winding mode turning tachyonic. This allows us to define and determine the exact Hagedorn temperature $\beta_H(\nu)$ for bosonic, type II and heterotic strings. 

Using the effective field theory for the thermal-winding mode around the $\nu$-dependent background, we find a novel `rotating string-star' saddle (perturbatively in the angular velocity) and study its properties. This configuration describes a self-gravitating bound state of highly excited rotating strings. As in the non-rotating case, the saddle qualitatively interpolates between the rotating strings phase and a rotating black hole.