Speaker
Elina Palmgren
(Helsinki institute of physics, Finland)
Description
This presentation will introduce the research [1] in which we employed the Planck CMB temperature anisotropy and lensing data, and baryon acoustic oscillation (BAO) data to constrain a phenomenological $w$CDM model, where dark matter and dark energy interact. We assumed time-dependent equation of state parameter for dark energy, and treated dark matter and dark energy as fluids whose energy-exchange rate is proportional to the dark-matter density. The CMB data alone leave a strong degeneracy between the interaction rate and the physical CDM density parameter today, $\omega_c$, allowing a large interaction rate $|\Gamma| \sim H_0$. However, the BAO data break this degeneracy. As a novelty we exploit the CMB lensing potential likelihood, which probes the matter perturbations at redshift $z\sim 2$ and is very sensitive to the growth of structure, and hence one of the tools for discerning between the $\Lambda$CDM model and its alternatives. In models with $w<-1$ the CMB and BAO data favour energy transfer from dark energy to dark matter at the rate of about 35\% of today's Hubble rate while the non-interacting model is 3$\sigma$ "disfavoured" by these data. Adding the CMB lensing data to the constraint budget, restores the non-interacting model to or near to the border of the 68\% CL region.
References
[1] J.Valiviita, E. Palmgren. arXiv:1504.02464. Accepted for publication in JCAP (2015).
