Noncommutative perturbative dynamics

We study the perturbative dynamics of noncommutative field theories on R-d, and find an intriguing mixing of the UV and the IR. High energies of virtu al particles in loops produce non-analyticity at low momentum. Consequently , the low energy effective action is singular at zero momentum even when th e original noncommutative field theory is massive. Some of the nonplanar di agrams of these theories are divergent, but we interpret these divergences as IR divergences and deal with them accordingly. We explain how this UV/IR mixing arises from the underlying noncommutativity. This phenomenon is rem iniscent of the channel duality of the double twist diagram in open string theory.