Abstract
The early cosmology, driven by a single scalar field, both massless and massive, in the context of Eddington-inspired Born-Infeld gravity, is explored. We show the existence of nonsingular solutions of bouncing and loitering type (depending on the sign of the gravitational theory’s parameter, ϵ) replacing the Big Bang singularity, and discuss their properties. In addition, in the massive case, we find some new features of the cosmological evolution depending on the value of the mass parameter, including asymmetries in the expansion/contraction phases, or a continuous transition between a contracting phase to an expanding one via an intermediate loitering phase. We also provide a combined analysis of cosmic chronometers, standard candles, BAO, and CMB data to constrain the model, finding that for roughly |ϵ|≲5·10−8m2 the model is compatible with the latest observations while successfully removing the Big Bang singularity. This bound is several orders of magnitude stronger than the most stringent constraints currently available in the literature.
Highlights
A way to parameterize dark energy is by using a scalar field, the so-called quintessence model or its generalizations to K-essence models, in such a way that the cosmological constant is replaced by a dark energy fluid with a nearly constant density [19,20,21,22,23]
Among the large pool of theories which have been investigated in the literature, for the sake of this paper, we present the proposal that was originally introduced by Banados and Ferreira [35] and dubbed Eddington-inspired Born-Infeld (EiBI) gravity (This proposal can be framed within the tradition of considering square-root action, such as in the DBI one, e.g., [36,37,38,39].)
We analyzed homogeneous and isotropic cosmological solutions in the context of Eddington-inspired Born–Infeld gravity coupled to a single scalar field
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. General Theory of Relativity (GR), including an early phase of inflationary expansion, a cold dark-matter component, and a tiny cosmological constant driving the accelerated late-time expansion of the Universe, has successfully met all observations [1,2] Within this model, scalar fields have found new and imaginative applications. The first one corresponds to bouncing solutions, where the universe contracts down to a minimum size before entering into an expansion phase, while the second are loitering solutions, which interpolate between an asymptotically Minkowski past and the current cosmological evolution For these nonsingular solutions, we carry out a combined analysis of cosmic chronometers, standard candles, BAO, and CMB data in order to constrain the EiBI parameter, finding the bound |e| .
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