Acceleration of the cosmic expansion induced by symmetry breaking

It is proved that in order to obtain a model of the accelerated cosmic expansion the thing one only need to do is to add a perturbation term to the Einstein-Hilbert Lagrangian. This term leads to some symmetry breaking terms in the fields equation, which makes the cosmic expansion accelerating. A vacuum de Sitter solution is obtained. A new explanation of the acceleration of the cosmic expansion is presented. In this model the changing of the expansion from decelerating to accelerating is an intrinsic property of the universe without need of an exotic dark energy. The acceleration of the cosmic expansion is induced by the symmetry breaking perturbation of the gravitational energy. The cosmological constant problem, the coincidence problem and the problem of phantom divide line crossing are naturally solved. The results of the model are roughly consistent with the observations.