The Largest Time Equation and Long Distance Behavior in Gauge Field Theories

Abstract

Unitarity and causality as expressed through the largest time equation are used to study soft and mass (collinear) singularities in gauge field theories. The origin and cancellation of these singularities in cross-sections is discussed both for abelian and non-abelian gauge theories. Exponentiation of soft divergences is also discussed in abelian theories. At the basis of this work on long distance behavior of gauge theories are certain diagrammatic identities that follow rather simply from the largest time equation. The discussion provides a unified treatment of soft divergencies and mass singularities and is common for both abelian and non-abelian gauge theories.