Prym curves with a vanishing theta-null

Carlos Maestro Pérez

If the theta-null divisor ${\Theta }_{\mathrm{null}}$ is moved to the Prym moduli space through the diagram ${\mathcal{S}}_g^{+}\to {\mathcal{M}}_g\leftarrow {\mathcal{R}}_g$, it splits i…