Cosmological Constraints on the Sign-Changeable Interactions

TL;DR

This paper investigates a new sign-changeable interaction model in dark energy and dark matter, constrained by recent observational data, revealing tight bounds on model parameters and supporting the possibility of sign change during cosmic evolution.

Contribution

It introduces a novel interaction model involving the deceleration parameter to allow sign change, and constrains it using latest observational data.

Findings

Model parameters are tightly constrained.

The key parameter β is confined to a narrow range.

Results support the sign-changeability of the interaction.

Abstract

Recently, Cai and Su [Phys. Rev. D {\bf 81}, 103514 (2010)] found that the sign of interaction $Q$ in the dark sector changed in the approximate redshift range of $0.45\,\lsim\, z\,\lsim\, 0.9$, by using a model-independent method to deal with the observational data. In fact, this result raises a remarkable problem, since most of the familiar interactions cannot change their signs in the whole cosmic history. Motivated by the work of Cai and Su, we have proposed a new type of interaction in a previous work [H. Wei, Nucl. Phys. B {\bf 845}, 381 (2011)]. The key ingredient is the deceleration parameter $q$ in the interaction $Q$, and hence the interaction $Q$ can change its sign when our universe changes from deceleration ($q>0$) to acceleration ($q<0$). In the present work, we consider the cosmological constraints on this new type of sign-changeable interactions, by using the latest observational data. We find that the cosmological constraints on the model parameters are fairly tight. In particular, the key parameter $\beta$ can be constrained to a narrow range.