Nonperturbative superpotentials from membrane instantons in heterotic M-theory

A formalism for calculating the open supermembrane contribution to the nonp erturbative superpotential of moduli in heterotic M-theory is presented. Th is is explicitly applied to the Calabi-Yau (1, 1)-moduli and the separation modulus of the end-of-the-world BPS three-branes, whose nonperturbative su perpotential is computed. The role of gauge bundles on the boundaries of th e open supermembranes is discussed in detail, and a topological criterion p resented for the associated superpotential to be nonvanishing. (C) 2001 Pub lished by Elsevier Science B.V.