Curvature-driven acceleration and a notion of vacuum in Nash theory

We discuss the cosmological implications in the Nash theory of gravity, where the field equations are derived from a lagrangian quadratic in Ricci invariants. A spatially homogeneous exact solution is found which can serve as a cosmological toy model. The implications of this model (departures from a standard Λ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Lambda$$\end{document}CDM cosmology) are compared with standard observational expectations, using a Markov chain Monte Carlo simulation of JLA+OHD+BAO\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$JLA + OHD + BAO$$\end{document} datasets. The Hubble evolution is satisfactory compared to the luminosity distance modulus measurements, and the evolution of deceleration parameter suggests an epoch of deceleration prior to the present acceleration. The redshift of transition is found to be quite satisfactory.