Refinements of Alon-Babai-Suzuki-type intersection theorems via non-shadows and binomial support
Abstract
We prove a multilevel non-shadow refinement of the Alon--Babai--Suzuki (ABS) nonuniform restricted-intersection theorem. Let and let be a set with . If is -intersecting and for every , then equivalently Thus the ABS bound is sharpened by the total non-shadow deficit on the top levels. In the modular setting, we take a coefficient-sensitive viewpoint: the polynomial method depends not just on the degree of the annihilator polynomial , but on which binomial terms actually appear in it. This yields a gap-free modular bound depending only on the active support levels of . For almost-initial residue patterns we obtain the collapse In particular, for consecutive residues we get the sharp bound , giving a partial negative answer to a question of Alon--Babai--Suzuki: the modular ABS bound is not attainable in the consecutive-residue regime whenever .
Keywords
Cite
@article{arxiv.2603.10309,
title = {Refinements of Alon-Babai-Suzuki-type intersection theorems via non-shadows and binomial support},
author = {Jiangdong Ai and Mingyu Liu},
journal= {arXiv preprint arXiv:2603.10309},
year = {2026}
}
Comments
version 2, 12 pages, fixed some typos and applied the binomial-support viewpoint to a non-modular setting