Hamiltonian of galileon field theory

TL;DR

This paper calculates the Hamiltonian of single galileon field theory, revealing energy properties of solutions and discussing ghost-like instabilities linked to the theory's nonlinear dynamics.

Contribution

It provides a detailed Hamiltonian calculation for galileon fields, including surface terms and energy analysis of static solutions with point sources.

Findings

Energy of two solution branches are equal in magnitude but opposite in sign.

Short-distance energy regularization occurs due to the cubic term despite divergent sources.

Negativity in energy is linked to ghost-like modes and nonlinear ghost instability.

Abstract

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 (ultra-violet) 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 ghost-like modes in the corresponding branch in the presence of the point source. This seems to be a non-linear manifestation of the ghost instability.