NONPERTURBATIVE MONODROMIES IN N=2 HETEROTIC STRING VACUA

We address non-perturbative effects and duality symmetries in N = 2 heterotic string theories in four dimensions. Specifically, we consider how each of the four lines of enhanced gauge symmetries in the perturbative moduli space of N = 2 T-2 compactifications is split into two lines where monopoles and dyons become massless. This amounts to considering non-perturbative effects originating from enhanced gauge symmetries at the microscopic string level. We show that the perturbative and non-perturbative monodromies consistently lead to the results of Seiberg-Witten upon identification of a consistent truncation procedure from local to rigid N = 2 supersymmetry.