A complete theory of smoothable compactified Jacobians of nodal curves

TL;DR

This paper introduces a new, broader class of compactified Jacobians for nodal curves, called V-compactified Jacobians, which generalize classical constructions and are characterized as limits of Jacobians under smoothings.

Contribution

It defines V-compactified Jacobians, extends the theory of limits of Jacobians, and broadens the class of known compactified Jacobians for nodal curves.

Findings

V-compactified Jacobians form a strictly larger class than classical ones.

V-compactified Jacobians can be characterized as limits of Jacobians of smooth curves.

The work extends previous theories to all compactified Jacobians.

Abstract

We introduce and study a new class of compactified Jacobians for nodal curves, that we call compactified Jacobians of vine type, or simply V-compactified Jacobians. This class is strictly larger than the class of classical compactified Jacobians, as constructed by Oda-Seshadri, Simpson, Caporaso and Esteves. We characterize V-compactified Jacobians as the compactified Jacobians that can arise as limits of Jacobians of smooth curves under a one-parameter smoothing of the nodal curve, extending previous works on fine compactified Jacobians by Pagani-Tommasi and Viviani to the case of all compactified Jacobians.