Axionic instantons and the creation of expanding universes

Abstract

Abstract In a class of models of scalar matter coupled to N = 1 supergravity, we investigate the existence of gravitational instantons that correspond to the creation of expanding universes. Expressing the derivatively coupled pseudoscalar field in terms of a second rank antisymmetric tensor field (axion), we show that, under mild assumptions about the scalar potential, the theory possesses axion-induced gravitational instanton solutions with the desired interpretation. The assumptions made can be met in the effective four-dimensional theory obtained in a particular compactification of the zero-slope limit of the ten-dimensional superstring theory. Such a system offers an appealing framework for the natural realization of the recent idea that coupling constants, including the cosmological constant, are determined by universal dynamics.