An attractive φ⁴ theory in light-front coordinates

We study an attractive $\phi^4$ interaction using Tamm-Dancoff truncation with light-front coordinates in $3+1$ dimensions. The truncated theory requires a coupling constant renormalization, we compute its $\beta$ function non-perturbatively, show that the model is asymptotically free, and find the corresponding Callan-Symanzik equations. The model supports bound states, we find the wave function for the ground state of the two-particle sector. We also give a bound for the $N$-particle ground state energy within a mean field approximation, including the corresponding result for the case of $2+1$ dimensions where the model does not require renormalization.