Quiver GIT for Varieties with Tilting Bundles

TL;DR

This paper demonstrates how varieties with tilting bundles can be reconstructed as quiver GIT quotients, providing new insights into their moduli spaces and applications to minimal models and surface singularities.

Contribution

It establishes conditions under which a variety with a tilting bundle is a fine moduli space for a quiver GIT, extending to cases without singularity restrictions.

Findings

Varieties with tilting bundles can be realized as quiver GIT quotients.

The method applies to flips, flops, and rational surface singularities.

Minimal resolutions of rational surface singularities can be constructed as quiver GIT moduli spaces.

Abstract

In the setting of a variety $X$ admitting a tilting bundle $T$ we consider the problem of constructing $X$ as a quiver GIT quotient of the endomorphism algebra $A=\textrm{End}_X(T)^{\textrm{op}}$ corresponding to the tilting bundle. We prove that if the tilting equivalence restricts to a bijection between the skyscraper sheaves of $X$ and the closed points of a quiver GIT moduli functor for $A$ then $X$ is indeed a fine moduli space for this quiver GIT moduli functor, and we prove this result without any assumptions on the singularities of $X$. As an application we consider varieties which are projective over an affine base such that the fibres are of dimension $\le 1$, and the pushforward of the structure sheaf on $X$ is the structure sheaf on the base. In this situation there is a particular tilting bundle on $X$ constructed by Van den Bergh, and our result allows us to reconstruct $X$ as a quiver GIT quotient for an easy to describe stability condition and dimension vector. This result applies to flips and flops in the minimal model program, and in the situation of flops shows that both a variety and its flop appear as quiver GIT moduli spaces for algebras produced from different tilting bundles on the variety. We also give an application to rational surface singularities, showing that their minimal resolutions can always be constructed as quiver GIT quotients for specific dimension vectors and stability conditions. This gives a construction of minimal resolutions as moduli spaces for all rational surface singularities, generalising the $G$-Hilbert scheme moduli space construction which exists only for quotient singularities.