Equitable [[2,10],[6,6]]-partitions of the 12-cube
Denis S. Krotov
TL;DR
This work completes the classification of unbalanced order-$7$ correlation-immune Boolean functions in $n=12$ variables by computer-aided classification of equitable $[[2,10],[6,6]]$-partitions of the $12$-cube, equivalently simple OA$(1536,12,2,7)$. The authors develop a refined, hierarchical search using local partitions, a reconstruction step via exact-cover, and a subdivision into square, heavy, and square-free subfamilies to manage computation, ultimately counting $103$ equivalence classes and identifying $2$ that are almost-OA$(1536,12,2,7+)$ while also cataloging $40$ pairs of disjoint OA$(1536,12,2,7)$. They analyze cycle structures, automorphism groups, and Fourier spectra to characterize properties and connect to known constructions, and they discuss related structures such as splitting into equitable $3$-partitions and the existence of non-simple OA$(1536,12,2,7)$. The results advance the understanding of the landscape of correlation-immune Boolean functions and their OA-counterparts, with implications for combinatorial design and cryptographic applications.
Abstract
We describe the computer-aided classification of equitable partitions of the $12$-cube with quotient matrix $[[2,10],[6,6]]$, or, equivalently, simple orthogonal arrays OA$(1536,12,2,7)$, or order-$7$ correlation-immune Boolean functions in $12$ variables with $1536$ ones (which completes the classification of unbalanced order-$7$ correlation-immune Boolean functions in $12$ variables). We find that there are $103$ equivalence classes of the considered objects, and there are only two almost-OA$(1536,12,2,8)$ among them. Additionally, we find that there are $40$ equivalence classes of pairs of disjoint simple OA$(1536,12,2,7)$ (equivalently, equitable partitions of the $12$-cube with quotient matrix $[[2,6,4], [6,2,4], [6,6,0]]$) and discuss the existence of a non-simple OA$(1536,12,2,7)$. Keywords: orthogonal arrays, correlation-immune Boolean functions, equitable partitions, perfect colorings, intriguing sets.
