Scalar-tensor gravity theory for dynamical light velocity

A gravity theory is developed with the metric (g) over cap(mu v) = g(mu v) + B partial derivative(mu)phi partial derivative(v)phi. In the present universe the additional contribution from the scalar field in the metric (g) over cap(mu v) can generate an acceleration in the expansion of the universe, without negative pressure and with a zero cosmological constant. In this theory, gravitational waves will propagate at a different speed from non-gravitational waves. It is suggested that gravitational wave experiments could test this observational signature. (C) 2000 Published by Elsevier Science B.V. All rights reserved.