McKay Correspondence for Canonical Orders

Canonical orders, introduced in the minimal model program for orders [CI05], are simultaneous generalisations of Kleinian singularities k[[s, t]], G < SL2 and their associated skew group rings k[[s, t]]∗G. In this paper, we construct minimal resolutions of canonical orders via non-commutative cyclic covers and skew group rings. This allows us to exhibit a derived equivalence between minimal resolutions of canonical orders and the skew group ring form of the canonical order in all but one case. The Fourier-Mukai transform used to construct this equivalence allows us to make explicit, the numerical version of the McKay correspondence for canonical orders noted in [CHI], which relates the exceptional curves of the minimal resolution to the indecomposable reflexive modules of the canonical order. We assume throughout this paper that everything is over an algebraically closed base field k of characteristic zero.