On Type IINS5-branes in the presence of an RR field

In this letter we use Type II NS5-branes in the presence of an RR field at the decoupling limit to study a non-commutative version of little string th eory. We shall see that the decoupling Limit of NS5-branes in the presence of an RR field is completely different from the one Lye had in ordinary lit tle string theory; in particular for Type IIA NS5-branes this decoupling li mit can be defined only when the theory is wrapped on a circle, but neverth eless flows to the ordinary non-compact (0,2) theory at the IR limit. We al so see that these theories, in the UV regime, where the non-commutative eff ects are important, can be described by smeared ordinary D3(D2)-branes in T ype IIB(A) string theory. (C) 2000 Elsevier Science B.V. All rights reserve d.