Some Cosmological Consequences of Non Trivial PPN Parameters $\beta$ and $\gamma$

TL;DR

This paper explores a graviton-dilaton cosmological model predicting finite curvature invariants and no big bang singularity, with implications for Brans-Dicke theory and inflation.

Contribution

It demonstrates a cosmological solution with non-trivial PPN parameters that avoids singularities and naturally produces a Brans-Dicke function compatible with inflation constraints.

Findings

Physical time extends indefinitely into past and future.

All curvature invariants remain finite, indicating no big bang singularity.

Emergence of a Brans-Dicke function suitable for hyperextended inflation.

Abstract

We study homogeneous isotropic universe in a graviton-dilaton theory obtained, in a previous paper, by a simple requirement that the theory be able to predict non trivial values for $\beta$ and/or $\gamma$ for a charge neutral point star, without any naked singularities. We find that in this universe the physical time can be continued indefinitely into the past or future, and that all the physical curvature invariants are always finite, showing the absence of big bang singularity. Adding a dilaton potential, we find again the same features. As a surprising bonus, there emerges naturally a Brans-Dicke function, which has precisely the kind of behaviour needed to make $\omega_{bd} ({\rm today}) > 500$ in hyperextended inflation.