Moment-graph formula conjecture for the Poincaré polynomial of a fundamental domain

Let FγF_{\gamma} be the fundamental domain equipped with the action of T~=T×Gm\widetilde{T}=T\times \mathbb{G}_{m}, and let Γ\Gamma be its moment graph, with vertices FγT~F_{\gamma}^{\widetilde{T}} and edges FγT~,1F_{\gamma}^{\widetilde{T},1}. For a total order o\mathfrak{o} on the vertices of Γ\Gamma, orient every edge so that its source is greater than its target. If nvon^{\mathfrak{o}}_{v} is the number of arrows with source vv, define

b2io={vΓ:nvo=i},b_{2i}^{\mathfrak{o}}=\sharp\{v\in\Gamma:n^{\mathfrak{o}}_{v}=i\},

and

Po(t)=ib2iot2i.P^{\mathfrak{o}}(t)=\sum_i b_{2i}^{\mathfrak{o}}t^{2i}.

Let P(t)P(t) be the Poincaré polynomial of FγF_{\gamma}.

Moment-graph formula conjecture. One has

P(t)=mino{Po(t)},P(t)=\min_{\mathfrak{o}}\{P^{\mathfrak{o}}(t)\},

where o\mathfrak{o} ranges over all total orders on the vertices of Γ\Gamma, and the minimum is taken with respect to the ordering in which P1(t)<P2(t)P_1(t)<P_2(t) when the leading coefficient of P2(t)P1(t)P_2(t)-P_1(t) is positive.

This conjectural formula would recover the Poincaré polynomial of the fundamental domain from its moment graph. The statement depends on the cohomological purity framework described immediately before it, but the source gives no resolution or further evidence for the conjecture.

Sources & referencesView supporting material

Primary source

Zongbin Chen, “Truncated affine Springer fibers and Arthur's weighted orbital integrals”, arXiv:1701.03202 (2021).

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