Variational calculation of the spectrum of two-dimensionalφ4theory in light-front field theory

Abstract

We demonstrate that a coherent state may be a valid vacuum in light-front field theory. Then by minimizing the sum of the expectation values of the light-front Hamiltonian and the momentum operators in a variational trial state, we evaluate the ground state (vacuum) of two-dimensional ${\ensuremath{\varphi}}^{4}$ field theory. The resulting expectation value in the coherent state is identical with the result of the effective-potential method in the equal-time formulation. Thus we demonstrate how to solve for the ground state of the strong-coupling (${\ensuremath{\varphi}}^{4}$${)}_{2}$ problem on the light front. We also discuss the calculation of excited states.