Perfect Forms and Torsion Bounds in Algebraic $K$-Theory over Totally Real and CM Fields

Abstract

We extend the method of Van Woerden \cite{woerden} to totally real and CM number fields to obtain an upper bound for the number of $\GLo-$equivalence classes of perfect forms. Moreover, by considering appropriate barycentric subdivisions of the Voronoi tessellation, we extend these estimates to the number of $\GLo$-orbits of $k$-dimensional faces of the Voronoi tessellation. As a consequence, we improve the asymptotic order of the bounds for the torsion part of $K_m(\rint)$ obtained by Soulé \cite{soule_hermitian_bounds} and Houriet \cite{Juliet_PHD}. We emphasise the improvement of the general bound for $F=\mathbb Q$, unchanged since Soulé's work, and the independence of the discriminant exponent from the field degree for totally real and CM fields.