Introduces a density variant of the Frankl-Rödl theorem, establishing bounds on vector pairs' probabilities in measurable subsets.
We establish a density variant of the Frankl-Rödl theorem on the sphere Sⁿ⁻¹, which concerns avoiding pairs of vectors with a specific distance, or equivalently, a prescribed inner product. In particular, we establish lower bounds on the probability that a randomly chosen pair of such vectors lies entirely within a measurable subset A ⊆ Sⁿ⁻¹ of sufficiently large measure. Additionally, we prove a density version of spherical avoidance problems, which generalize from pairwise avoidance to broader configurations with prescribed pairwise inner products. Our framework encompasses a class of configurations we call inductive configurations, which include simplices with any prescribed inner product $-1 < r < 1$. As a consequence of our density statement, we show that all inductive configurations are sphere Ramsey.
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Guruswami et al. (2025) studied this question.
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