Near Hagedorn Dynamics of NS Fivebranes, or A New Universality Class of Coiled Strings

We analyze the thermodynamics of NS 5-branes as the temperature approaches the NS 5-branes’ Hagedorn temperature, and conclude that the dynamics of Little String Theory'' is a new universality class of interacting strings. First we point out how to vary the temperature of the near extremal solution by taking into account $g_s$ corrections. The Hagedorn temperature is shown to be a limiting temperature for the theory. We then compare the thermodynamics to that of a toy model made of free strings and find basic discrepancies. This suggests a need for a new class of string interactions. We suggest that this new universality class is characterized by a strong attractive self-intersection interaction, which causes strings to be coiled. This model might also explain why Little String Theories’’ exist in at most 5+1 dimensions.