paper

Cosmology of the interacting Cubic Galileon

arXiv:1807.00700

Abstract

We consider the cosmological dynamics of the cubic Galileon field model interacting with dark matter, where the interaction between the cosmic dark sectors is proportional to Hubble parameter and dark energy density. The background field equations are converted into an autonomous dynamical system of first order equations using suitable dimensionless variables. The fixed points are determined and their stability analyzed by means of the eigenvalue method. The analysis of the stability of the fixed points along that of the avoidance of ghosts and Laplacian instabilities implies negative coupling parameter. We find an attractor fixed point in the de Sitter phase, and construct an approximated tracker solution, which to a good approximation, mimics the background cosmic evolution obtained by solving numerically the autonomous system of equations. In addition, we perform the statefinder and Om diagnostics and show that for some appropriate values of the coupling constant and initial conditions, the trajectories in the statefinder parameter phase space evolves towards a stable state corresponding to Λ CDM model. The comparison with the observed distance modulus and Hubble parameter data sets clearly indicates that the cosmological dynamics of the interacting cubic model is compatible with the existence of an interaction between the dark sectors.

30 pages, 9 fugures

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