Cosmological model with dynamical curvature

The recently introduced relativistic Lagrangian darkon fluid model (EPJ C (2015) 75:9) is generalized to a self-gravitating, irrotational, pressure-less and stress free geodesic fluid, whose energy-momentum tensor is dust-like with nontrivial energy flow, defining the general framework for our cosmological model. In the present paper we consider only the averaged dynamics of the Universe at very large scales, allowing us to work with conformal flat geometry. The corresponding covariant propagation and constraint equations are treated in a shear-free nonrelativistic limit. The dynamics is described with a Lagrangian in minisuperspace. Analytic solutions for the energy density, the Hubble function and the 1st order relativistic correction to the spatial curvature are obtained by means of two conditional dynamical symmetries. This leads to a cosmological model where the accelerated expansion of the Universe is driven by a time-dependent spatial curvature without the need for introducing any kind of dark energy. A differential equation for the area distance is derived in addition.