arXiv:2611.11488 · v1

A note on exact external information complexity

首次提交 2026-11-09 00:29

版本更新 2026-11-09 00:29

雷达观测 2026-11-10 12:16

摘要

We study the prior-free zero-error private-coin external information complexity $B(f)$ of finite two-party functions, with correctness on every input. An elementary rectangle/entropy argument gives $B(\mathsf{AND})=\log_2 3$. A complete classification of Boolean $3\times3$ matrices leaves, up to input permutations and output complementation, only the two-overlapping-rectangles function $F$ without an exact value. An entropy potential and a finite rational protocol give $2.1212661667060486842\ldots\le B(F)<2.130998318$. We also determine its deterministic external information and zero-error communication costs. A separate product-prior certificate and internal-information additivity yield $R_0^{\mathrm{pub}}(F^{\times t})\ge2.021991187178562\ldots\,t$, strictly exceeding the fractional-cover rate $2t$.