English

FKN, first proof, rewritten

Combinatorics 2021-05-10 v1

Abstract

About twenty years ago we wrote a paper, "Boolean Functions whose Fourier Transform is Concentrated on the First Two Levels", \cite{FKN}. In it we offered several proofs of the statement that Boolean functions f(x1,x2,,xn)f(x_1,x_2,\dots,x_n), whose Fourier coefficients are concentrated on the lowest two levels are close to a constant function or to a function of the form f=xkf=x_k or f=1xkf=1-x_k. Returning to the paper lately, we noticed that the presentation of the first proof is rather cumbersome, and includes several typos. In this note we rewrite that proof, as a service to the public.

Keywords

Cite

@article{arxiv.2105.03246,
  title  = {FKN, first proof, rewritten},
  author = {Ehud Friedgut and GIl Kalai and Assaf Naor},
  journal= {arXiv preprint arXiv:2105.03246},
  year   = {2021}
}
R2 v1 2026-06-24T01:52:34.257Z