Comments on noncommutative perturbative dynamics

We analyze further the IR singularities that appear in noncommutative field theories on R-d. We argue that all IR singularities in nonplanar one loop diagrams may be interpreted as arising from the tree level exchanges of new light degrees of freedom, one coupling to each relevant operator. These ex changes are reminiscent of closed string exchanges in the double twist diag rams in open string theory. Some of these degrees of freedom are required t o have propagators that are inverse linear or logarithmic. We suggest that these can be interpreted as free propagators in one or two extra dimensions respectively. We also calculate some of the IR singular terms appearing at two loops in noncommutative scalar field theories and find a complicated m omentum dependence which is more difficult to interpret.