On the distribution of shapes of sextic pure number fields
Anuj Jakhar, Ravi Kalwaniya, Anwesh Ray, Bidisha Roy
TL;DR
This work analyzes the distribution of shapes for pure sextic number fields K = \\mathbb{Q}(\\sqrt[6]{m}) ordered by discriminant. By partitioning into 20 Types via local conditions at 2 and 3 and computing explicit integral bases, the authors express each shape as a fixed Type-specific conjugation of a triple (λ1, λ2, λ3). They prove equidistribution of shapes on translated torus orbits in the shape space \\mathcal{S}_5, with limiting measures that split into continuous and discrete components, and they provide an analogous distribution result for the discrete parameters (a5/a1, a3, a2a4). The methodology blends geometry-of-numbers with analytic sieve methods to count lattice points subject to arithmetic constraints, yielding precise asymptotics and local factors. The results illuminate a new phenomenon in shape statistics and lay groundwork for extending to higher-degree pure fields or other structured families.
Abstract
The shape of a number field $K$ of degree $n$ is defined as the equivalence class of the lattice of integers with respect to linear operations that are composites of rotations, reflections, and positive scalar dilations. The shape is a point in the space of shapes $\mathscr{S}_{n-1}$, which is the double quotient $\mathrm{GL}_{n-1}(\mathbb{Z}) \backslash \mathrm{GL}_{n-1}(\mathbb{R}) / \mathrm{GO}_{n-1}(\mathbb{R})$. We investigate the distribution of shapes of pure sextic number fields $K=\mathbb{Q}(\sqrt[6]{m})$, ordered by absolute discriminant. Such fields are partitioned into $20$ distinct Types determined by local conditions at $2$ and $3$, and an explicit integral basis is given in each case. For each Type, the shape of $K$ admits an explicit description in terms of shape parameters. Fixing the sign of $m$ and a Type, we prove that the corresponding shapes are equidistributed along a translated torus orbit in the space of shapes. The limiting distribution is given by an explicit measure expressed as the product of a continuous measure and a discrete measure.
