A new holographic dark energy model in Brans-Dicke theory with logarithmic scalar field

We study a holographic dark energy model in the framework of Brans-Dicke (BD) theory with taking into account the interaction between dark matter and holographic dark energy. We use the recent observational data sets, namely SN Ia compressed Joint Light-Analysis (cJLA) compilation, Baryon Acoustic Oscillations (BAO) from BOSS DR12 and the Cosmic Microwave Background (CMB) of Planck 2015. After calculating the evolution of the equation of state as well as the deceleration parameters, we find that with a logarithmic form for the BD scalar field the phantom crossing can be achieved in the late time of cosmic evolution. Unlike the conventional theory of holographic dark energy in standard cosmology (omega(D) = 0), our model results in a late time accelerated expansion. It is also shown that the cosmic coincidence problem may be resolved in the proposed model. We execute the statefinder and Om diagnostic tools and demonstrate that interaction term does not play a significant role. Based on the observational data sets used in this paper it seems that the best value with 1 sigma and 2 sigma confidence interval are Omega(m) = 0.268(-0.007)(-0.009)(+ 0.008)(+ 0.010) , alpha = 3.361(-0.401)(-0.522)(+0.332)(+0.483) , beta = 5.560(-0.510)(-0.729)(+0.541)(+0.780) , c = 0.777(-0.017)(-0.023)(+0.023)(+0.029) and b(2) = 0.045, according to which we find that the proposed model in the presence of interaction is compatible with the recent observational data.