The Hagedorn transition in noncommutative open string theory

The Hagedorn transition in noncommutative open string theory (NCOS) is rela tively simple because gravity decouples. For NCOS theories in no more than five space-time dimensions, the Hagedorn transition is second order, and th e high temperature phase involves long, nearly straight fundamental strings separating from the D-brane on which the NCOS theory is defined. Above fiv e spacetime dimensions interaction effects become important below the Haged orn temperature. Although this complicates studies of the transition, we be lieve that the high temperature phase again involves long strings liberated from the bound state. (C) 2001 American Institute of Physics.