English

On a refinement of the Ahlswede--Katona Theorem

Combinatorics 2026-02-10 v2

Abstract

A classical theorem of Ahlswede and Katona determines the maximum density of the 22-edge star in a graph with a given edge density. Motivated by its application in hypergraph Tur\'{a}n problems, we establish a refinement of their result under the additional assumption that the graph contains a large independent set in which every vertex has high degree.

Keywords

Cite

@article{arxiv.2510.19681,
  title  = {On a refinement of the Ahlswede--Katona Theorem},
  author = {Jianfeng Hou and Xizhi Liu and Yixiao Zhang},
  journal= {arXiv preprint arXiv:2510.19681},
  year   = {2026}
}

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26 pages, comments are welcome