Rational Points in Hyperbolic Regions and Multiplicative Diophantine Approximation on Manifolds
Sam Chow, Rajula Srivastava, Niclas Technau, Han Yu
TL;DR
This work develops a comprehensive convergence theory for multiplicative Diophantine approximation on smooth non-degenerate manifolds and certain affine subspaces under a generic Diophantine condition. The authors reduce curved cases to non-degenerate curves via a fibring lemma and treat the flat case using quantitative non-divergence estimates for spaces of lattices, together with detailed harmonic-analytic counting in anisotropic regions. The main results establish Gallagher-type convergence for the ambient Lebesgue measure on manifolds and for affine subspaces satisfying Hypothesis D, resolving longstanding questions and sharpening extremality results. The methodology combines target-hitting arguments, dyadic decompositions, Poisson summation, oscillatory integral bounds, and robust non-divergence machinery, with careful accounting of parameter dependencies across the flat/curved dichotomy. These results advance our understanding of rational points near manifolds and provide a versatile framework for multiplicative Diophantine problems in non-flat geometric settings.
Abstract
We establish the convergence theory of multiplicative Diophantine approximation for all non-degenerate, smooth manifolds. We also settle said convergence theory for all affine subspaces satisfying a highly generic and essentially optimal Diophantine condition. This answers a question of Beresnevich and Velani from 2005, while simultaneously sharpening results of Kleinbock and Margulis on the strong extremality of non-degenerate manifolds, and of Kleinbock on the strong extremality of affine subspaces.
