Closed strings tachyons and non-commutative instabilities

21 pags.We observe a relation between closed strings tachyons and one-loop instabilities in non-supersymmetric non-commutative gauge theories. In particular we analyze the spectra of type-IIB string theory on C3/ZN orbifold singularities and the non-commutative field theory that lives on D3 branes located at the singularity. We find a surprising correspondence between the existence or not of one-loop low-momentum instabilities in the noncommutative field theory and the existence or not of tachyons in the closed string twisted sectors. Moreover, the relevant piece of the non-commutative field theory effective action is suggestiv e of an exchange of closed string modes. This suggests that non-commutative field theories retain some information about the dynamics of the underlying string configuration. Finally, we also comment on a possible relation between closed string tachyon condensation and field theory tachyon condensation.Peer reviewe