M-theory on a Calabi-Yau manifold

We compactify M-theory on a Calabi-Yau manifold to five dimensions by wrapping the membrane and fivebrane solitons of the eleven-dimensional supergravity limit around Calabi-Yau two-cycles and four-cycles, respectively. We identify the perturbative and non-perturbative BPS states thus obtained with those of heterotic string theory compactified on K3 × S1. Quantum aspects of the five-dimensional theory are discussed.