Abstract
Modes with zero longitudinal light-front momentum (zero modes) do have roles
to play in the analysis of light-front field theories. These range from
improvements in convergence for numerical calculations to implications for the
light-front vacuum and beyond to fundamental issues in the connection with
equal-time quantization. In particular, the discrepancy in values of the
critical coupling for $\phi^4_{1+1}$ theory, between equal-time and light-front
quantizations, would appear to be resolvable with the proper treatment of zero
modes and near-zero modes. We provide a survey of these issues and point to
open questions.