Solvable points on intersections of quadrics, cubics, and quartics

Abstract

Let $k$ be a field of characteristic not 2 or 3. We establish polynomial lower bounds on the ambient dimension $N$ for an intersection $X\subset\mathbb{P}^N$ of quadrics, cubics and quartics to have a dense collection of solvable points, i.e. points in $X(k^{\mathsf{Sol}})$ where $k^{\mathsf{Sol}}/k$ is a solvable closure. Our method connects the classical theory of polar hypersurfaces, as redeveloped by Sutherland, to Fano varieties $\mathcal{F}(j,X)$ of $j$-dimensional linear subspaces on $X$, and we use this to obtain improved control on the arithmetic of $\mathcal{F}(j,X)$.