Scalar field unification of interacting viscous dark fluid from a geometrical scalar–tensor theory of gravity

• Published in: PHYSICS OF THE DARK UNIVERSE 2020-12, Vol.30, p.100706, Article 100706
• Main Authors: Madriz Aguilar, José Edgar, Gil-Ocaranza, A., Montes, M., Zamarripa, J.
• Format: Article
• Language: English
• Subjects: Accelerated cosmic expansion; Dark energy and dark matter; Scalar–tensor gravity; Viscous interacting dark fluid; Weyl-Integrable geometry
• ISSN: 2212-6864; 2212-6864
• DOI: 10.1016/j.dark.2020.100706

We investigate, in the framework of a recently introduced new class of invariant geometrical scalar–tensor theory of gravity, the possibility that a viscous dark fluid can be described in a unified manner by a single scalar field. Thus we developed a model in which both the metric tensor and the scalar field have geometrical origin. The scalar field is characterized by a non-canonical kinetic term and the scalar viscosity of the dark fluid appears as soon the kinetic energy of the scalar field is no longer canonical. The scalar viscosity is considered as a function of the Hubble and the deceleration parameters. To illustrate the formalism we have considered two cases: a constant and a thermodynamic equation of state parameters. In the both cases we obtain analytic representations for the scalar field and their respective potentials. We delimit free parameters by comparing with some Planck 2018 results.