Zero momentum modes in discrete light-cone quantization

We consider the constrained zero modes found in the application of discrete light-cone quantization 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 discrete light-cone quantization, namely, zero-mode loops.