Moduli of roots of line bundles on curves

Abstract

We treat the problem of completing the moduli space for roots of line bundles on curves. Special attention is devoted to higher spin curves within the universal Picard scheme. Two new different constructions, both using line bundles on nodal curves as boundary points, are carried out and compared with pre-existing ones.

Final version, added references. To appear in Trans. Amer. Math. Soc