Given a Boolean function $f:{-1,1}^nto {-1,1}$, the Fourier distribution assigns probability $widehat{f}(S)^2$ to $Ssubseteq [n]$. The Fourier Entropy-Influence (FEI) conjecture of Friedgut and Kalai asks if there exist a universal constant C>0 such that $H(hat{f}^2)leq C Inf(f)$, where $H(hat{f}^2)$ is the Shannon entropy of the Fourier distribution of $f$ and $Inf(f)$ is the total influence of $f$. 1) We consider the weaker Fourier Min-entropy-Influence (FMEI) conjecture. This asks if $H_{infty}(hat{f}^2)leq C Inf(f)$, where $H_{infty}(hat{f}^2)$ is the min-entropy of the Fourier distribution. We show $H_{infty}(hat{f}^2)leq 2C_{min}^oplus(f)$, where $C_{min}^oplus(f)$ is the minimum parity certificate complexity of $f$. We also show that for every $epsilongeq 0$, we have $H_{infty}(hat{f}^2)leq 2log (|hat{f}|_{1,epsilon}/(1-epsilon))$, where $|hat{f}|_{1,epsilon}$ is the approximate spectral norm of $f$. As a corollary, we verify the FMEI conjecture for the class of read-$k$ $DNF$s (for constant $k$). 2) We show that $H(hat{f}^2)leq 2 aUC^oplus(f)$, where $aUC^oplus(f)$ is the average unambiguous parity certificate complexity of $f$. This improves upon Chakraborty et al. An important consequence of the FEI conjecture is the long-standing Mansours conjecture. We show that a weaker version of FEI already implies Mansours conjecture: is $H(hat{f}^2)leq C min{C^0(f),C^1(f)}$?, where $C^0(f), C^1(f)$ are the 0- and 1-certificate complexities of $f$, respectively. 3) We study what FEI implies about the structure of polynomials that 1/3-approximate a Boolean function. We pose a conjecture (which is implied by FEI): no flat degree-$d$ polynomial of sparsity $2^{omega(d)}$ can 1/3-approximate a Boolean function. We prove this conjecture unconditionally for a particular class of polynomials.
تحميل البحث