Massless radiation from heavy rotating string and Kerr/string correspondence

We calculate emission rates of a massless state from a highly excited rotating string in perturbative bosonic open string theory. By averaging huge degeneracies of initial string states with specifying the mass and a single component of the angular momentum, we find thermal spectrum in a wide range of the angular momentum. We derive the temperature that characterizes the thermal spectrum from the partition function of a single rotating string from which we also find the entropy and the angular velocity of rotating strings. We also argue based on these quantities the Horowitz-Polchinski correspondence principle between rotating strings/Kerr black holes for non-extremal as well as extremal cases. In the parameter region where the Kerr black holes exist, the thermal spectrum is comparable to scalar emissions from a rotating black hole.