Duality Between the Webs of Heterotic and Type II Vacua

We discuss how transitions in the space of heterotic K3×T 2 compactifications are mapped by duality into transitions in the space of Type II compactifications on Calabi–Yau manifolds. We observe that perturbative symmetry restoration, as well as non-perturbative processes such as changes in the number of tensor multiplets, have at least in many cases a simple description in terms of the reflexive polyhedra of the Calabi–Yau manifolds. Our results suggest that to many, perhaps all, four-dimensional N = 2 heterotic vacua there are corresponding type II vacua. 1 [email protected]. 2 [email protected]. On sabbatical leave from Departamento de F́ısica, Facultad de Ciencias, Universidad Central de Venezuela.