Compactifying the rank two Hitchin system via spectral data on semistable curves

TL;DR

This paper constructs a compactification of the rank two Hitchin system using spectral data on semistable curves, extending classical spectral correspondence to a broader, compactified setting.

Contribution

It introduces a new compactification of the Hitchin system via spectral data on semistable curves, generalizing classical spectral correspondence to the compactified case.

Findings

Provides a compactification of the Hitchin base using quadratic multi-scale differentials.

Extends spectral correspondence to the compactified Hitchin system.

Establishes a correspondence between torsion-free sheaves and Higgs pairs on admissible covers.

Abstract

We study resolutions of the rational map to the moduli space of stable curves that associates with a point in the Hitchin base the spectral curve. In the rank two case the answer is given in terms of the space of quadratic multi-scale differentials introduced in [BCGGM3]. This space defines a compactification (of the projectivization) of the regular locus of the $\mathrm{GL}(2,\mathbb{C})$-Hitchin base and provides a compactification of the Hitchin system by compactified Jacobians of pointed stable curves. We show how the classical $\mathrm{GL}(2,\mathbb{C})$- and $\mathrm{SL}(2,\mathbb{C})$-spectral correspondence extend to the compactified Hitchin system by a correspondence along an admissible cover between torsion-free rank $1$ sheaves and (multi-scale) Higgs pairs of rank $2$.