The categorical McKay correspondence conjecture for finite simply-laced Dynkin diagrams

Let II be a simply-laced Dynkin diagram with Coxeter number hh. A triangulated category D\mathcal{D} is equipped with an exact twist functor FF(2)\mathcal{F}\mapsto\mathcal{F}(-2).

Categorical McKay correspondence conjecture. There exists such a category and functor satisfying all of the following: D\mathcal{D} is 2-periodic, with T2=idT^2=\operatorname{id}; every object has a canonical functorial isomorphism F(2h)F\mathcal{F}(2h)\cong\mathcal{F}; and, for the Grothendieck group KK equipped with the inner product defined in the source, the indecomposable objects form a simply-laced root system whose Coxeter element is C ⁣:[F][F(2)]C\colon[\mathcal{F}]\mapsto[\mathcal{F}(-2)]. Choosing a parity function p ⁣:IZ2p\colon I\to\mathbb{Z}_2 with p(i)=p(j)+1p(i)=p(j)+1 on adjacent vertices, the indecomposables are naturally bijective with

I^={(i,n)I×Z2hp(i)+n0(mod2)},\widehat{I}=\{(i,n)\in I\times\mathbb{Z}_{2h}\mid p(i)+n\equiv0\pmod 2\},

with C(i,n)=(i,n2)C(i,n)=(i,n-2), and are denoted Xi(n)X_i(n). Their Hom and Ext groups, path-algebra description, and the equivalences RΦh ⁣:DDb(I,Ωhop)/T2R\Phi_h\colon\mathcal{D}\to D^b(I,\Omega_h^{op})/T^2 for every height function h ⁣:IZ2hh\colon I\to\mathbb{Z}_{2h} satisfy precisely properties (5) and (6) of the conjecture in the source.

This conjecture proposes a finite-type analogue of the categorical construction of affine root systems arising from the McKay correspondence. It predicts a category whose indecomposable objects encode the root system and whose twist realizes the Coxeter element; the source provides the detailed Hom, Ext, quiver, and derived-equivalence requirements but does not state a resolution.

Sources & referencesView supporting material

Primary source

Alexander Kirillov and Jaimal Thind, “Coxeter Elements and Periodic Auslander-Reiten Quiver”, arXiv:math/0703361 (2007).

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