A Hurwitz divisor on the Moduli of Prym curves
Andrei Bud
TL;DR
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Abstract
For genus $g=2i\geq4$ and the length $g-1$ partition $μ= (4,2,\ldots,2,-2,\ldots,-2)$ of 0, we compute the first coefficients of the class of $\overline{D}(μ)$ in $\mathrm{Pic}_\mathbb{Q}(\overline{\mathcal{R}}_g)$, where $D(μ)$ is the divisor consisting of pairs $[C,η]\in \mathcal{R}_g$ with $η\cong \mathcal{O}_C(2x_1+x_2+\cdots + x_{i-1}-x_i-\cdots-x_{2i-1})$ for some points $x_1,\ldots, x_{2i-1}$ on $C$. We further provide several enumerative results that will be used for this computation.
