Galashin–Lam's deformation-retract and filtration conjecture for open positroid varieties

Let kk and nn be coprime positive integers, let Xk,n∘X^\circ_{k,n} denote the top-dimensional open positroid variety, and let Jk,n−kJ_{k,n-k} be the compactified Jacobian of the plane curve singularity xk=yn−kx^k=y^{n-k}. A deformation retract is understood in the topological sense, without requiring it to be algebraic.

Galashin–Lam's conjecture. There exists a non-algebraic deformation retract

r:Xk,n∘→Jk,n−kr:X^\circ_{k,n}\to J_{k,n-k}

from Xk,n∘X^\circ_{k,n} onto Jk,n−kJ_{k,n-k}. Moreover, in compactly supported cohomology,

r∗:Hc∗(Jk,n−k)→Hc∗(Xk,n∘)r^*:H_c^*(J_{k,n-k})\to H_c^*(X^\circ_{k,n})

sends the weight filtration to the perverse filtration.

This conjecture connects the topology and filtrations of the open positroid variety with those of the compactified Jacobian of a plane curve singularity. The supplied text attributes the motivation to work of Galashin–Lam and to the works cited as STZ17 and STWZ19, but gives no resolution status.

References

Primary source

Calvin Yost-Wolff, “Point Count of the Top-dimensional Open Positroid Variety”, arXiv:2602.15316 (2026).

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