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arXiv · 2601.18738

Roth-type theorems in $K_{s,t}$-free sets

Yifan Jing·Cosmin Pohoata·Max Wenqiang Xu
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Abstract

We show that for all integers $2\le s\le t$, any $K_{s,t}$-free subset of $[N]$ with size $\Omega(n^{1-1/s})$ must contain a nontrivial solution to every fixed translation-invariant linear equation in at least five variables. This extends earlier results for Sidon sets due to Conlon-Fox-Sudakov-Zhao and Prendiville to the full family of $K_{s,t}$-free sets. We also study the corresponding problem in vector spaces over finite fields. In $\mathbb F_q^n$ we obtain stronger quantitative bounds, including polylogarithmic savings, by combining Fourier-analytic transference with polynomial-method input from the arithmetic cycle-removal lemma of Fox-Lov\'asz-Sauermann.

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Yifan Jing, Cosmin Pohoata, Max Wenqiang Xu. 2026-01-26. Roth-type theorems in $K_{s,t}$-free sets. https://arxiv.org/abs/2601.18738

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