Inequivalent vacua in quantum field theory

Implementing a path integral quantization of real massive scalar fields in a wide class of curved spaces we derive a general expression for the vacua in the Schrodinger representation. Using the general boundary formulation of quantum theory, we show how a symmetry of the space of classical solutions leads to a one-parameter family of quantum vacua. In this way we offer a new derivation of the alpha-vacua in de Sitter space.