Virtual resolutions of points in $\mathbb{P}^1 \times \mathbb{P}^1$

Abstract

We explore explicit virtual resolutions, as introduced by Berkesch, Erman, and Smith, for ideals of sets of points in $\mathbb{P}^1 \times \mathbb{P}^1$. Specifically, we describe a virtual resolution for a sufficiently general set of points $X$ in $\mathbb{P}^1 \times \mathbb{P}^1$ that only depends on $|X|$. We also improve an existence result of Berkesch, Erman, and Smith in the special case of points in $\mathbb{P}^1 \times \mathbb{P}^1$; more precisely, we give an effective bound for their construction that gives a virtual resolution of length two for any set of points in $\mathbb{P}^1 \times \mathbb{P}^1$.