The GKM-pair character conjecture for Braden–MacPherson sheaves

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Let G^{\widehat{\mathcal G}} be the affine moment graph, let w∈V=W^w\in\mathcal V={\widehat{\mathcal W}}, and let (K,w)(K,w) be a GKM-pair. For the Braden–MacPherson sheaf B(w){\mathscr B}(w), define

h(B(w)):=∑x≤wrk⁡′ B(w)xvl(w)Tx,h({\mathscr B}(w)):=\sum_{x\le w}{{\operatorname{rk}}}^\prime\,{\mathscr B}(w)^x v^{l(w)}T_x,

where, for a graded free SS-module M≅⨁i=1nS{li}M\cong\bigoplus_{i=1}^n S\{l_i\}, rk⁡′M:=vl1+⋯+vln{{\operatorname{rk}}}^\prime M:=v^{l_1}+\dots+v^{l_n}. Let H‾w\underline{H}_w denote the self-dual affine Kazhdan–Lusztig basis element of the affine Hecke algebra associated with ww. The GKM-pair character conjecture. If (K,w)(K,w) is a GKM-pair, then

h(B(w))=H‾w.h({\mathscr B}(w))=\underline{H}_w.

This conjecture predicts that the graded character of the Braden–MacPherson sheaf agrees with the corresponding affine Kazhdan–Lusztig basis element whenever the pair satisfies the GKM condition. It links moment-graph sheaves with affine Hecke-algebra combinatorics; the supplied text does not state whether it has been resolved.

References

Primary source

Peter Fiebig, “An upper bound on the exceptional characteristics for Lusztig's character formula”, arXiv:0811.1674 (2009).

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