Noncommutativity from the string perspective: modification of gravity at ammwithoutmmsized extra dimensions

We explore how the IR pathologies of noncommutative field theory are resolvedwhen the theory is realized as open strings in background B-fields:essentially, since the IR singularities are induced by UV/IR mixing, stringtheory brings them under control in much the same way as it does the UVsingularities. We show that at intermediate scales (where the Seiberg-Wittenlimit is a good approximation) the theory reproduces the noncommutative fieldtheory with all the (un)usual features such as UV/IR mixing, but that outsidethis regime, in the deep infra-red, the theory flows continuously to thecommutative theory and normal Wilsonian behaviour is restored. The resultinglow energy physics resembles normal commutative physics, but with additionalsuppressed Lorentz violating operators. We also show that the phenomenon ofUV/IR mixing occurs for the graviton as well, with the result that, inconfigurations where Planck's constant receives a significant one-loopcorrection (for example brane-induced gravity), the distance scale below whichgravity becomes non-Newtonian can be much greater than any compact dimensions.Comment: 30 pages. Slight revision: clarified some points and added a referenc