Cosmological constraints on the sign-changeable interactions

Recently, Cai and Su [Phys. Rev. D 81 (2010) 103514] found that the sign of interaction Q in the dark sector changed in the approximate redshift range of 0.45 ≲ z ≲ 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 845 (2011) 381]. 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 β can be constrained to a narrow range.