Linear series on a curve of compact type bridged by a chain of elliptic curves

Abstract

In the present paper we investigate conditions for the non-existence of a limit linear series on a curve of compact type such that two smooth curves are bridged by a chain of two elliptic curves. Combining this work with results on the existence of a smoothable limit linear series on such a curve, we show relations among Brill-Noether loci of codimension at most two in the moduli space of complex curves. Specifically, Brill-Noether loci of codimension two have mutually distinct supports.