Interacting Dark Energy and Dark Matter: observational Constraints from Cosmological Parameters

TL;DR

This work tests an interacting holographic dark energy/dark matter model against precision cosmology, employing a holographic energy density $\rho_D = 3 c^2 M_p^2 / L^2$ and a dark-sector interaction $Q = 3 b^2 H(\rho_m + \rho_D)$. By combining age measurements, high-redshift object ages, dark matter perturbation growth, and low-ℓ CMB data, the authors constrain the coupling $b^2$ (requiring it to be nonzero) and the holographic parameter $c$, with robust lower bounds on $b^2$ (roughly $0.05$) and a preference for $c>1$ from CMB considerations. The analysis shows that the interacting model can accommodate the existence of an old quasar at high redshift and yields a notably better fit to the COBE/WMAP low-ℓ spectrum than the standard $\Lambda$CDM model, supporting the possibility that energy exchange in the dark sector plays a significant role in cosmic evolution. Overall, the paper argues that dark-energy/dark-matter interaction is essential to describe the observed universe within the holographic framework, and it outlines concrete parameter ranges for future observational tests.

Abstract

Several observational constraints are imposed on the interacting holographic model of Dark Energy and Dark Matter. First we use the age parameter today, as given by the WMAP results. Subsequently, we explained the reason why it is possible, as recently observed, for an old quasar to be observed in early stages of the universe. We discuss this question in terms of the evolution of the age parameter as well as in terms of the structure formation. Finally, we give a detailed discussion of the constraints implied by the observed CMB low $\ell$ suppression. As a result, the interacting holographic model has been proved to be robust and with reasonable bounds predicts a non vanishing interaction of Dark Energy and Dark Matter.

Figures (9)

• Figure 1: The age of the universe as a function of the (constant) parameter defined by the equation of state. The shadowed region is the total age at $z=0$ got by WMAPwmapcosmos
• Figure 2: Dimensionless age parameter as a function of redshift for simple dark energy models. We have takenthe following parameters: $H_0=76.2 Km/s/Mpc, \Omega_D=0.76$ in (a), $H_0=69.6 Km/s/Mpc, \Omega_D=0.76$ in (b), $H_0=76.2 Km/s/Mpc, \Omega_D=0.68$ in (c) and $H_0=69.6 Km/s/Mpc, \Omega_D=0.68$ in (d). All curves cross the shadowed area yielding an age parameter smaller than the value $2.1 Gyr$ required by the quasar APM 08279+5255.
• Figure 3: Age of the universe as a function of the redshift for interacting holographic dark energy models. The shadowed region is the total age at $z=0$ observed from WMAP wmapcosmos. In (a) we considered $\Omega_k=0$; in (b) $\Omega_k=0.019$.
• Figure 4: Dimensionless age parameter as a function of redshift for interacting holographic dark energy models. In (a) we considered $\Omega_k=0$, in (b) $\Omega_k=0.019$. We see that for appropriately coupling between dark energy and dark matter, the interacting holographic dark energy model can accommodate the existance of APM08279+5255 system.
• Figure 5: The constrained parameter space of $b^2$ and $c$. The dark grey is the constraint from the total age at $z=0$ from WMAP wmapcosmos, the light grey is the constraint from the old quasar APM08279+5255 0608 and the dark region is the parameter space compatible with the $w_D$ crossing $-1$12 and the age constraints. We have taken $\Omega_k=0, \Omega_D=0.76$ in (a), $\Omega_k=0, \Omega_D=0.68$ in (b), $\Omega_k=0.019, \Omega_D=0.76$ in (c) and $\Omega_k=0.019, \Omega_D=0.68$ in (d).