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

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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)≤C⋅I(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.

References

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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