BIRATIONAL EQUIVALENCES OF VORTEX MODULI

WE CONSTRUCT a finite-dimensional Kahler manifold with a holomorphic, symplectic circle action whose symplectic reduced spaces may be identi fied with the tau-vortex moduli spaces (or tau-stable pairs). The Mors e theory of the circle action induces natural birational maps between the reduced spaces for different values of tau which in the case of ra nk two bundles can be canonically resolved in a sequence of blow-ups a nd blow-downs. Copyright (C) 1996 Elsevier Science Ltd