Nonsinglet Sector of $c=1$ Matrix Model and 2D Black Hole

Abstract

Extending our recent work (\arXiv{\tt hep-th/0310106}) we study the nonsinglet sector of $c=1$ matrix model by renormalization group analysis for a gauged matrix quantum mechanics on circle with an appropriate gauge breaking term to incorporate the effect of world-sheet vortices. The flow equations indicate BKT phase transition around the self-dual radius and the nontrivial fixed points of the flow exhibit black hole like phases for a range of temperatures beyond the self-dual point. One class of fixed point interpolate between $c=1$ for $R > 1$ and $c=0$ as $R \to 0$ via black hole phase that emerges after the phase transition. The other two classes of nontrivial fixed points also develop black hole like behavior beyond R=1. From a thermodynamic study of the free energy obtained from the Callan-Symanzik equations we show that all these unstable phases do have negative specific heat. The thermodynamic quantities indicate that the system does undergo a first order phase transition near the Hagedorn temperature, around which the new phase is formed, and exhibits one loop finite energy correction to the Hagedorn density of states. The flow equations also suggest a deformation of the target space geometry through a running of the compactification radius where the scale is given by the dilaton. Remarkably there is a regime where cyclic flow is observed.