# Codimension one distributions and stable rank 2 reflexive sheaves on threefolds

## TL;DR

This paper investigates the stability of tangent sheaves of codimension one distributions with isolated singularities on certain threefolds, and applies these results to the moduli space of stable rank 2 reflexive sheaves, providing new characterizations and constructions.

## Contribution

It establishes stability criteria for tangent sheaves of distributions on threefolds and characterizes components of the moduli space of stable rank 2 reflexive sheaves, including construction methods.

## Key findings

- Stable tangent sheaves for distributions with isolated singularities.
- Characterization of irreducible components of the moduli space of stable rank 2 reflexive sheaves.
- Determination of connected components of singular schemes for distributions with non-isolated singularities.

## Abstract

We show that codimension one distributions with at most isolated singularities on certain smooth projective threefolds with Picard rank one have stable tangent sheaves. The ideas in the proof of this fact are then applied to the characterization of certain irreducible components of the moduli space of stable rank 2 reflexive sheaves on $\mathbb{P}^3$, and to the construction of stable rank 2 reflexive sheaves with prescribed Chern classes on general threefolds. We also prove that if $\mathscr{G}$ is a subfoliation of a codimension one distribution $\mathscr{F}$ with isolated singularities, then $Sing(\mathscr{G})$ is a curve. As a consequence, we give a criterion to decide whether $\mathscr{G}$ is globally given as the intersection of $\mathscr{F}$ with another codimension one distribution. Turning our attention to codimension one distributions with non isolated singularities, we determine the number of connected components of the pure 1-dimensional component of the singular scheme.