Directed KKL inequality

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Let f ⁣:{0,1}n→{0,1}f\colon\{0,1\}^n\to\{0,1\} be a Boolean function. Define its distance to monotonicity by

ε(f):=min⁡g monotonePr⁡x∼{0,1}n[f(x)≠g(x)].\varepsilon(f):=\min_{g\ \mathrm{monotone}}\Pr_{x\sim\{0,1\}^n}[f(x)\neq g(x)].

For i∈[n]i\in[n], define the negative influence of coordinate ii on ff by

Inf⁡i−[f]:=#{x:f(x)>f(x⊕i) and x≼x⊕i}⋅12n−1.\operatorname{Inf}^{-}_i[f]:=\#\{x:f(x)>f(x^{\oplus i})\text{ and }x\preccurlyeq x^{\oplus i}\}\cdot\frac{1}{2^{n-1}}.

Directed KKL inequality. Given a Boolean function f ⁣:{0,1}n→{0,1}f\colon\{0,1\}^n\to\{0,1\}, there exists i∈[n]i\in[n] such that

Inf⁡i−[f]≥Ω(ε(f)⋅log⁡nn).\operatorname{Inf}^{-}_i[f]\geq\Omega\left(\varepsilon(f)\cdot\frac{\log n}{n}\right).

This is the natural directed analogue of the Kahn–Kalai–Linial inequality, with distance to monotonicity replacing variance and negative influences replacing ordinary influences. The supplied material does not establish whether the inequality is proved or remains open.

References

Primary source

Quentin Dubroff, Shivam Nadimpalli and Bhargav Narayanan, “A Counterexample to a Directed KKL Inequality”, arXiv:2210.02035 (2022).

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