Two-dimensional light-front $\phi^4$ theory in a symmetric polynomial basis

TL;DR

This paper investigates the spectrum of 1+1 dimensional $\

Contribution

It introduces a symmetric polynomial basis for light-front Hamiltonian diagonalization, improving convergence analysis in $\

Findings

Converged spectra for various Fock sectors.

Estimated critical coupling for positive mass squared.

Resolved discrepancy with equal-time calculations.

Abstract

We study the lowest-mass eigenstates of $\phi^4_{1+1}$ theory with both odd and even numbers of constituents. The calculation is carried out as a diagonalization of the light-front Hamiltonian in a Fock-space representation. In each Fock sector a fully symmetric polynomial basis is used to represent the Fock wave function. Convergence is investigated with respect to the number of basis polynomials in each sector and with respect to the number of sectors. The dependence of the spectrum on the coupling strength is used to estimate the critical coupling for the positive-mass-squared case. An apparent discrepancy with equal-time calculations of the critical coupling is resolved by an appropriate mass renormalization.