Friedgut–Kalai Fourier-Entropy-Influence conjecture for the uniform cube

From papers

Let f:({0,1}n,μ1/2n){±1}f:(\{0,1\}^n,\mu_{1/2}^n)\to\{\pm1\} be Boolean-valued, with spectral entropy

Ent1/2(f)=S[n]f^(S)2log(1f^(S)2){\rm Ent}_{1/2}(f)=\sum_{S\subset[n]}\hat f(S)^2\log\left(\frac{1}{\hat f(S)^2}\right)

and total influence I(1/2)[f]=i=1nInfi(1/2)[f]{\rm I}^{(1/2)}[f]=\sum_{i=1}^n{\rm Inf}_i^{(1/2)}[f]. Friedgut–Kalai's FEI conjecture. There exists a universal constant C>0C>0 such that for every nn and every Boolean function f:({0,1}n,μ1/2n){±1}f:(\{0,1\}^n,\mu_{1/2}^n)\to\{\pm 1\},

Ent1/2(f)CI(1/2)[f].{\rm Ent}_{1/2}(f) \le C\cdot {\rm I}^{(1/2)}[f].

This is a longstanding open problem concerning upper bounds for Fourier entropy in terms of influence on the uniform discrete cube.

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Sources & referencesView supporting material

Primary source

Fan Chang, “A Lower Bound for the Fourier Entropy of Boolean Functions on the Biased Hypercube”, arXiv:2511.07739 (2026).

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