UV/IR mixing, noncommutative instabilities and closed strings

The leading UV/IR mixing effects on noncommutative field theories modify the dispersion relations and, depending on their sign, may cause the appearance of unstable modes. For noncommutative gauge theories on D-branes, this phenomenon is able to capture important information about the closed string spectrum of the parent string theory. We analyse noncommutative D-branes on nonsupersymmetric orbifolds and twisted circle backgrounds. We find that the sign of the leading UV/IR mixing effects is governed by the mass gap between the lowest modes in the NSNS and RR closed string towers. For noncommutative D3-branes at orbifolds we obtain a stronger result: a one to one correspondence between noncommutative instabilities and closed string tachyons. (Abstract Copyright [2004], Wiley Periodicals, Inc.)