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, and let $\ell \leqslant pn$ be a nonnegative integer. We prove that if $\mathcal {F},\mathcal {G}\subseteq \{0,1\}^n$ are two families whose cross intersections forbid $\ell $—that is, they satisfy $|A\cap B|\neq \ell $ for every $A\in \mathcal {F}$ and every $B\in \mathcal {G}$ – then, setting $t:= \min \{\ell ,pn-\ell \}$, we have the subgaussian bound $$\begin{align*}\mu_p(\mathcal{F})\, \mu_{p'}(\mathcal{G}) \leqslant 2\exp\Big( - \frac{t^2}{58^2\,pn}\Big), \end{align*}$$where $\mu _p$ and $\mu _{p'}$ denote the p-biased and $p'$-biased measures on $\{0,1\}^n$, respectively.
Karamanlis, Miltiadis; Dodos, Pandelis. Forbidden sparse intersections. Forum of Mathematics, Sigma, Tome 13 (2025) no. 1, p. e99. doi: 10.1017/fms.2025.10067
@article{10_1017_fms_2025_10067,
author = {Karamanlis, Miltiadis and Dodos, Pandelis},
title = {Forbidden sparse intersections},
journal = {Forum of Mathematics, Sigma},
pages = {e99},
year = {2025},
volume = {13},
number = {1},
doi = {10.1017/fms.2025.10067},
url = {http://geodesic.mathdoc.fr/articles/10.1017/fms.2025.10067/}
}
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