Non-minimal Effective Scalar-Tensor Gravity in the Early Universe

Abstract

We study the consistency of several early-Universe scenarios within a framework of non-minimal effective sca\-lar--ten\-sor gravity. We show that bounce, inflation, and genesis stages are supported within the aforementioned theory. Consequently, this framework can serve as a viable model of the early Universe, where accelerated expansion is driven by the theory's own intrinsic degrees of freedom. Notably, the theory also provides two different values of the Hubble parameter, potentially explaining the different values of the Hubble constant measured from galaxy clusters and relic radiation, respectively.

Figures (2)

• Figure 1: Three-dimensional parameter space $(\alpha,\beta,v)$ for $\tilde{g}\in[-0.8,-0.4]$, where $v\equiv\dfrac{\tilde{g}^2}{\lambda^2\kappa^2}$. Other parameters are $\lambda=1$ and $\kappa^2=32\pi$.
• Figure 2: Phase space classification in the $(\alpha,\beta)$ plane for three values of $\tilde{g}$: (a) $\tilde{g}=-0.8$, (b) $\tilde{g}=-0.6$, (c) $\tilde{g}=-0.4$, where $v\equiv\dfrac{\tilde{g}^2}{\lambda^2\kappa^2}$. Other parameters are $\lambda=1$ and $\kappa^2=32\pi$.