Little strings on Dn orbifolds

We explore two classes of 6d N = (1, 0) little string theories obtained from type IIA/IIB NS5-branes probing D-n singularities. Their tensor branches are described by effective gauge theories whose instanton solitons are macroscopic little strings. We specifically study two families of 2d N = (0, 4) gauge theories which describe at low energy the worldsheet dynamics of the type IIA/IIB little strings. These gauge theories are useful to calculate the supersymmetric partition functions of the little string theories on R-4 x T-2. We establish the T-duality of the little string theories by utilizing their BPS spectra as a probe.