Nonsingular cosmological models in a scalar-tensor theory of gravity

Several homogeneous and isotropic space-time models free from singularities are discussed which were obtained on the basis of a gauge-invariant five-dimensional theory of gravity. It is noted that when certain additional assumptions are made, this theory may be interpreted as a geometric variant of a Jordan-Brans-Dicke type of scalar-tensor theory. The models discussed include a nonsingular closed isotropic model, a nonsingular open isotropic model, and open as well as closed models in which total mass is not conserved. Numerical values are derived for the critical density of the universe in each model.