Hamiltonian of Galileon field theory

We give a detailed calculation for the Hamiltonian of single Galileon field theory, keeping track of all the surface terms. We calculate the energy of static, spherically symmetric configuration of the single Galileon field at cubic order coupled to a point source and show that the 2-branches of the solution possess energy of equal magnitude and opposite sign, the sign of which is determined by the coefficient of the kinetic term alpha(2). Moreover, the energy is regularized in the short distance (ultraviolet) regime by the dominant cubic term even though the source is divergent at the origin. We argue that the origin of the negativity is due to the ghostlike modes in the corresponding branch in the presence of the point source. This seems to be a nonlinear manifestation of the ghost instability.