Representations on canonical models of generalized Fermat curves and their syzygies

Abstract

We study canonical models of ${\left(\mathbb{Z}/k\mathbb{Z}\right)}^n$- covers of the projective line, tamely ramified at exactly $n+1$ points each of index $k$, when $k,n\ge 2$ and the characteristic of the ground field $K$ is either zero or does not divide $k$. We determine explicitly the structure of the respective homogeneous coordinate ring first as a graded $K$-algebra, next as a ${\left(\mathbb{Z}/k\mathbb{Z}\right)}^n$- representation over $K$, and then as a graded module over the polynomial ring; in the latter case, we give generators for its first syzygy module, which we also decompose as a direct sum of irreducible representations.