Nonperturbative renormalization group in light-front three-dimensional real scalar model

The three-dimensional real scalar model, in which the $Z_2$ symmetry spontaneously breaks, is renormalized in a nonperturbative manner based on the Tamm-Dancoff truncation of the Fock space. A critical line is calculated by diagonalizing the Hamiltonian regularized with basis functions. In the broken phase the canonical Hamiltonian is tachyonic, so the field is shifted as running mass and coupling so that the mass of the ground state vanishes. The marginal ($\phi^6$) coupling dependence of the critical line is weak