Cosmology with interaction in the dark sector

TL;DR

The paper investigates a cosmological model where dark matter and dark energy interact via a coupling parameter $\epsilon$, modifying dark matter dilution to $\rho_{dm} = \rho_{dm,0} a^{-3+\epsilon}$. It provides a scalar-field realization with potential $V(\phi)$ that reproduces the same dynamics, using a constant $x$ to link kinetic energy to the interaction. Using a joint analysis of SN Ia data from SNLS and Constitution, BAO from 2dFGRS/SDSS, and $H(z)$ measurements, it finds that both positive and negative $\epsilon$ are allowed, with thermodynamic constraints in the vacuum case favoring $\epsilon \ge 0$. The results indicate that an interacting dark sector is viable and motivates extensions with a redshift-dependent coupling and more precise data.

Abstract

Unless some unknown symmetry in Nature prevents or suppresses a non-minimal coupling in the dark sector, the dark energy field may interact with the pressureless component of dark matter. In this paper, we investigate some cosmological consequences of a general model of interacting dark matter-dark energy characterized by a dimensionless parameter $ε$. We derive a coupled scalar field version for this general class of scenarios and carry out a joint statistical analysis involving SNe Ia data ({Legacy} and {Constitution} sets), measurements of baryon acoustic oscillation peak at $z = 0.20$ (2dFGRS) and $z = 0.35$ (SDSS), and measurements of the Hubble evolution $H(z)$. For the specific case of vacuum decay ($w = -1$), we find that, although physically forbidden, a transfer of energy from dark matter to dark energy is favored by the data.

Figures (2)

• Figure 1: Left: The ratio $\rho_{de}/\rho_{dm}$ as a function of the redshift parameter $z$ [Eqs. (\ref{['dm']}) and (\ref{['de']})] for some selected values of $\epsilon$ and $w$ and $\Omega_{de,0}/\Omega_{dm,0} \simeq 3$. Note that, for large and positive values of $\epsilon$, the relative contribution of dark energy to dark matter may be significant at early times. Right: The potential $U(\Phi)$ [Eqs. (\ref{['ph']})-(\ref{['va']})] as a function of the field for some selected values of $w$ and $\epsilon = 0.1$ and $\Omega_{dm} = 0.23$. In this Panel, "NB" means that the baryons participate of the interacting process whereas "WB" means that they were regarded as a separetely conserved component contributing with $\Omega_{b,0} = 0.0416$.
• Figure 2: Contours of $\chi^2$ in the planes $w - \epsilon$ (left), $\Omega_{dm,0} - \epsilon$ (middle) and $\Omega_{dm,0} - \epsilon$ with $w = -1$ (right). These contours are drawn for $\Delta \chi^2 = 2.30$ and $6.17$. In all Panels, dashed lines correspond to the joint analysis involving SNLS + BAO + H($z$) measurements whereas the solid ones to CS + BAO + H($z$) data. The shadowed area in the Panel at right stands for the thermodynamical constraint on $\epsilon$ discussed in Ref. alc.