Unitarity of Time-Like Noncommutative Gauge Theories: The Violation of Ward Identities in Time-Ordered Perturbation Theory
arXiv:hep-th/0309021 · doi:10.1016/j.nuclphysb.2003.10.022
Abstract
We study Ward identities for simple processes with external gauge bosons in the time-ordered perturbation theory approach to time-like noncommutative gauge theories. We demonstrate that these Ward identities cannot be satisfied when all orders in the noncommutativity parameters theta_i0 are taken into account. We conclude that in time-ordered perturbation theory one cannot solve the unitarity problem of time-like noncommutative quantum field theories.
16 pages LaTeX (feynmp.sty, elsart.cls and thophys.sty included). Clarified the comments on Seiberg-Witten Maps, updated references. This version has been accepted for publication in Nuclear Physics B