Deformations of canonical triple covers

Abstract

In this paper, we show that if $X$ is a smooth variety of general type of dimension $m\ge 3$ for which the canonical map induces a triple cover onto $Y$, where $Y$ is a projective bundle over ${\mathbf{P}}^1$ or onto a projective space or onto a quadric hypersurface, embedded by a complete linear series, then the general deformation of the canonical morphism of $X$ is again canonical and induces a triple cover. The extremal case when $Y$ is embedded as a variety of minimal degree is of interest, due to its appearance in numerous situations. This is especially interesting as well, since it has no lower dimensional analogues.