$p$-torsion for unramified Artin--Schreier covers of curves

Bryden Cais, Douglas Ulmer

Let $Y\to X$ be an unramified Galois cover of curves over a perfect field $k$ of characteristic $p>0$ with $\mathrm{Gal}(Y/X)\cong \mathbb{Z}/p\mathbb{Z}$, and let $J_X$ and $J_Y$ b…