On the Prym map of degree 4 cyclic covers of genus 2 curves

Abstract: In this paper, we study the Prym map associated to degree 4 \'etale cyclic covers of genus 2 curves. We show that its non-empty fibers, apart from two exceptional fibers, are isomorphic to the intersection of an elliptic normal curve in $\mathbb{P}^3$ with an affine space $\mathbb{A}^3 \subset \mathbb{P}^3$. Moreover, we obtain a new description of the space of degree 4 \'etale cyclic covers of genus 2 curves $\mathcal{R}_2^4$ and find equations of elliptic and hyperelliptic curves arising from such covers.