The cornering and GIT-specialisation diagram for Kleinian quiver varieties

Let 0∈J⊆J′⊆I0 \in J \subseteq J' \subseteq I, set K≔I∖JK \coloneqq I \setminus J and K′≔I∖J′K' \coloneqq I \setminus J', and let σK,K′\sigma_{K,K'} be the cone defined by

σK,K′≔{θ∈Θnδ;∣;θ(δ)≥0;,θ(αj)≥(n−1)θ(δ)for;j∈J∖0;,θ(αk)≥0for;k∈K∖K′;,θ(αk)=0for;k∈K′;.}.\sigma_{K,K'} \coloneqq \left\{\theta \in \Theta_{n\delta} \\; \Bigg| \\; \begin{matrix*}[l] \theta(\delta) \geq 0 \\;, & \\ \\\\ \theta(\alpha_j) \geq (n-1)\theta(\delta) & \text{for} \\; j \in J \setminus \\{0\\} \\;, \\\\ \theta(\alpha_k) \geq 0 & \text{for} \\; k \in K \setminus K' \\;, \\\\ \theta(\alpha_k) = 0 & \text{for} \\; k \in K' \\;. \end{matrix*} \right\}.

Let h∗E⁡J′h_*\operatorname{\mathcal{E}}_{J'} and h∗V⁡J′h_*\operatorname{\mathcal{V}}_{J'} be the cornered algebra and module, and write Quot⁡J,J′v\operatorname{Quot}_{J,J'}^v for the corresponding Quot scheme. The cornering and GIT-specialisation conjecture. If θ∈CK\theta \in C_K, θ′\theta' lies in the relative interior of σK\sigma_K, and θ”\theta” lies in the relative interior of σK,K′\sigma_{K,K'}, then there is a commutative diagram

\begin{tikzcd} \operatorname{Quot}_J^{n \delta} \arrow[r, "\sim"] \arrow[d] & \operatorname{\mathfrak{M}}_{\theta}(n \delta,w) \arrow[d] \\\\ \operatorname{Quot}_{J,J'}^{n \delta} \arrow[r, "\sim"] \arrow[d] & \operatorname{\mathfrak{M}}_{\theta”}(n \delta,w) \arrow[d] \\\\ \operatorname{Hilb}^n(X_J) \arrow[r, "\sim"] & \operatorname{\mathfrak{M}}_{\theta'}(n \delta,w), \end{tikzcd}

in which all morphisms are birational and projective, the horizontal morphisms are isomorphisms induced by g∗g_*, the left vertical morphisms are induced by cornering at J′J' and JJ, respectively, and the right vertical morphisms arise from GIT specialisation. This conjectures an interpolation between the Quot scheme, the intermediate cornered Quot scheme, and the Hilbert scheme, matching the corresponding Nakajima quiver varieties.

References

Primary source

Lukas Bertsch and Ruth Wye, “Stacky Resolutions of Kleinian Singularities and Nakajima Quiver Varieties”, arXiv:2509.22569 (2026).

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