Zero momentum modes in discrete light-cone quantization

TL;DR

This paper demonstrates that including zero momentum modes in discrete light-cone quantization enhances nonperturbative quantum field theory calculations by improving convergence and enabling direct vacuum expectation value computations.

Contribution

It shows that zero modes, often neglected in DLCQ, can be included straightforwardly and are beneficial for accurate nonperturbative spectral calculations.

Findings

Including zero modes improves numerical convergence.

Zero modes enable direct calculation of vacuum expectation values.

Zero-mode loops are a separate contribution not covered by DLCQ.

Abstract

We consider the constrained zero modes found in the application of discrete light-cone quantization (DLCQ) to the nonperturbative solution of quantum field theories. These modes are usually neglected for simplicity, but we show that their inclusion can be relatively straightforward, and, what is more, that they are useful for nonperturbative calculations of field-theoretic spectra. In particular, inclusion of zero modes improves the convergence of the numerical calculation and makes possible the direct calculation of vacuum expectation values, even when the zero modes are determined dynamically. We also comment on zero-mode contributions not included by DLCQ, namely zero-mode loops.