Holographic dark energy with cosmological constant

Inspired by the multiverse scenario, we study a heterotic dark energy model in which there are two parts, the first being the cosmological constant and the second being the holographic dark energy, thus this model is named the AHDE model. By studying the AHDE model theoretically, we find that the parameters d and Omega(hde) are divided into a few domains in which the fate of the universe is quite different. We investigate dynamical behaviors of this model, and especially the future evolution of the universe. We perform fitting analysis on the cosmological parameters in the AHDE model by using the recent observational data. We find the model yields chi(2)(min) = 426.27 when constrained by Planck + SNLS3 + BAO + HST, comparable to the results of the HDE model (428.20) and the concordant ACDM model (431.35). At 68.3% CL, we obtain -0.07 < Omega(A0) < 0.68 and correspondingly 0.04 < Omega(hde0) < 0.79, implying at present there is considerable degeneracy between the holographic dark energy and cosmological constant components in the AHDE model.