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On the measure of primitive representations of an integer by a quadratic form

Manabu Murata

Vol. 344 (2026), No. 1, 69–102
Abstract

We explicitly compare a measure defined by Siegel with a mass defined by Shimura, both in the context of primitive representations of an integer by an indefinite integral quadratic form. The main result gives an explicit formula for the Siegel’s measure under the assumption that the lattices are maximal. The result is applied to the computation of these measures in some families, such as that of hyperbolic forms.

Keywords
quadratic Diophantine equation, quadratic form, primitive representation
Mathematical Subject Classification
Primary: 11D09, 11E12
Secondary: 11E20
Milestones
Received: 8 February 2025
Revised: 14 April 2026
Accepted: 11 May 2026
Published: 10 August 2026
Authors
Manabu Murata
Department of Electrical and Electronic Engineering
Ritsumeikan University
Kusatsu
Japan

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