A toric degeneration of Kronecker moduli spaces

Abstract: In this paper, we show that there is a finite SAGBI basis of the coordinate ring of a Kronecker quiver moduli space, indexed by primitive semi-standard tableaux pairs. This induces a toric degeneration of the Kronecker moduli space to a normal toric variety, a generalization of the toric degeneration of the Grassmannian to the Gelfand--Cetlin polytope constructed by Gonciulea--Lakshmibai. The moment polytope of the degenerate toric variety can be described as the intersection of two Gelfand--Cetlin polytopes. We explain when this can be generalized to degenerations coming from matching fields.