Littlewood's conjecture

Let (α,β)(\alpha,\beta) be a pair of real numbers, and let ϵ>0\epsilon>0. The system

{p+qαr+qβ<ϵ/TqT\begin{cases} |p+q\alpha||r+q\beta|<\epsilon/T\\ q\leq T \end{cases}

uses solutions (p,r,q)Z×Z×N(p,r,q)\in\mathbb{Z}\times\mathbb{Z}\times\mathbb{N} for an unbounded set of T>0T>0. Littlewood's conjecture. For every pair (α,β)(\alpha,\beta) and every ϵ>0\epsilon>0, there is an unbounded set of T>0T>0 for which the system has a solution. Almost every pair satisfies this property, and the set of multiplicatively badly approximable pairs has zero Hausdorff dimension, but the conjecture remains unresolved.

Sources & referencesView supporting material

Primary source

Dmitry Kleinbock and Chengyang Wu, “Simultaneously bounded and dense orbits for commuting Cartan actions”, arXiv:2509.05272 (2025).

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