DMS Algebra Seminar

Speaker: Jayan Mukherjee (Oklahoma State University)

Title: Syzygies of ribbons on higher genus curves

Abstract: In this talk, we will discuss the syzygies of the canonical embedding of a ribbon \(\widetilde{C}\) on a curve \(C\) of genus \(g \geq 1\). We show that the linear series Clifford index and the resolution Clifford index are equal for a general ribbon of arithmetic genus \(p_a\) on a general curve of genus \(g\) with \(p_{a} \geq \operatorname{max}\{3g+7, 6g-4\}\). Among non-general ribbons, the case of split ribbons is particularly interesting. Equality of the two Clifford indices for a split ribbon is related to the gonality conjecture for \(C\) and it implies Green's conjecture for all double covers \(C'\) of \(C\) with \(g(C') \geq \textrm{max}\{3g+2, 6g-4\}\). We reduce it to the vanishing of certain Koszul cohomology groups of an auxiliary module of syzygies associated to \(C\) , which may be of independent interest.