Causality, current algebra, and fixed poles
A-M. M. Abdel-Rahman, Waleed Ahmed, M. O. Taha · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields · 1974
We study the causality restrictions on the structure of the nonforward matrix element of the commutator of two conserved isovector currents. We give a fixed-pole interpretation of the noncausal contribution, derive a set of causality and current-algebra sum rules, and determine the structure of the equal-time commutator.