VORTICES IN HIGH-TEMPERATURE STRING THEORY
George Chapline, Frans R. Klinkhamer · Modern Physics Letters A · 1989
We discuss the role of XY-like vortices on the world-sheet for the free energy of strings at high temperatures. There is a Kosterlitz-Thouless phase transition at the Hagedorn temperature, above which the vortices contribute to the free energy in genus zero and generate a mass gap. We speculate that high-temperature “string” theory could be essentially discrete.