Isochronous cosmologies (Q2925871)

This paper defines a new type of cosmology, an isochronous cosmology, in analogy with non-relativistic, isochronous many-body problems. For simplicity only homogeneous and isotropic metrics are considered. The models are cyclic and they are termed isochronous since the duration of the cycles does not depend on the initial conditions. The models are locally Friedmann-Robertson-Walker, but not globally, since the time reparameterization is not a diffeomorphism in this case. An interesting property of these cosmologies is the fact that they can be geodesically complete and hence singularity free, whether they are physically realistic is controversial as the authors note.