THERMODYNAMICS OF VORTICES IN THE PLANE

The thermodynamics of vortices in the critically coupled Abelian Higgs model, defined on the plane, are investigated by placing N vortices i n a region of the plane with periodic boundary conditions: a torus. It is noted that the moduli space for N vortices, which is the same as t hat of N indistinguishable points on a torus, fibrates into a CP(N-1) bundle over the Jacobi manifold of the torus. The volume of the moduli space is a product of the area of the base of this bundle and the vol ume of the fiber. These two values are determined by considering two 2 -surfaces in the bundle corresponding to a rigid motion of a vortex co nfiguration, and a motion around a fixed center of mass. The partition function for the vortices is proportional to the volume of the moduli space, and the equation of state for the vortices is P(A-4pi N) = NT in the thermodynamic limit, where P is the pressure, A the area of the region of the plane occupied by the vortices, and T the temperature. There is no phase transition.