Accelerated expansion by non-minimally coupled scalar fields

Abstract

In a class of spatially homogeneous cosmologies including those of Bianchi type I--VIII mathematical results are presented which show that a scalar field non-minimally coupled to the scalar curvature of spacetime can dynamically yield a positive cosmological constant without the potential being required to include one. More precisely, it is shown that in an exponential potential any positive coupling constant leads eventually to late-time de Sitter expansion and isotropization corresponding to a positive cosmological constant and that this behaviour is independent of the steepness of the potential. This is in marked contrast to the minimally coupled case where power-law inflation occurs at most, provided the potential is sufficiently shallow.