arXiv subjects

Elsa M. Teixeira

Publications and source records attributed to Elsa M. Teixeira.

20 records · Page 2Linked to original sources

arXiv2020

Disformally Coupled Quintessence

In this work we consider a cosmological model in which dark energy is portrayed by a canonical scalar field which is allowed to couple to the other species by means of a disformal transformation of the metric. We revisit the current literature by assuming that the disformal function in the metric transformation can depend both on the scalar field itself and on its derivatives, encapsulating a wide variety of scalar-tensor theories. This generalisation also leads to new and richer phenomenology, explaining some of the features found in previously studied models. We present the background equations and perform a detailed dynamical analysis, from where new disformal fixed points emerge, that translate into novel cosmological features. These include early scaling regimes between the coupled species and broader stability parameter regions. However, viable cosmological models seem to have suppressed disformal late-time contributions.

gr-qc↗

arXiv2019

Conformally Coupled Tachyonic Dark Energy

We present and study a conformally coupled dark energy model, characterised by an interaction between a tachyon field $ϕ$, with an inverse square potential $V (ϕ)$, and the matter sector. A detailed analysis of the cosmological outcome reveals different possibilities, in contrast with the previously studied uncoupled model, for which there exists only one stable critical point that gives late-time acceleration of the Universe. The introduction of the coupling translates into an energy exchange between the fluids. We find the interesting possibility of the emergence of a new fixed point, which is a scaling solution and an attractor of the system. In this case, it is possible to describe an everlasting Universe with $Ω_ϕ \simeq 0.7$, therefore alleviating the cosmic coincidence problem. However, we find that, in order for the evolution to be cosmologically viable, there is the need to introduce one uncoupled matter species, dominant at early times.

gr-qc↗