A complete degeneration of the moduli of $G$-bundles on a curve

Abstract

For a semi simple group G it is known the moduli stack of principal G-bundles over a fixed nodal curve is not complete. Finding a completion requires compactifying the group G. However it was shown in [34] that this is not sufficient to complete the moduli stack over a family of curves. In this paper I describe how to use an embedding of the loop group LG to provide a completion of the stack of G-bundles over a one dimensional family of curves degenerating to a nodal curve. The completion comes with a modular interpretation inspired by the work of Gieseker, Seshadri, Kausz and Thaddeus and Martens.