English

New Sidorenko-type inequalities in tournaments

Combinatorics 2025-12-15 v1

Abstract

As a directed analog of Sidorenko's conjecture in extremal graph theory, Fox, Himwich, Zhou, and the second author defined an oriented graph HH to be tournament Sidorenko (anti-Sidorenko) if the random tournament asymptotically minimizes (maximizes) the number of copies of HH among all tournaments. We prove new inequalities of this form for oriented trees and cycles, considering both local and global notions of the Sidorenko property. We make progress on a conjecture of the aforementioned authors that every tree has an anti-Sidorenko direction, and give a characterization of short paths. For long paths we show that orientations are split symmetrically between being locally Sidorenko and anti-Sidorenko, yet almost all orientations are not globally Sidorenko. Finally, we give algorithms characterizing the local Sidorenko status of paths and cycles when the number of vertices is not divisible by four.

Keywords

Cite

@article{arxiv.2512.11222,
  title  = {New Sidorenko-type inequalities in tournaments},
  author = {Xiaoyu He and Nitya Mani and Jiaxi Nie and Nathan Tung and Fan Wei},
  journal= {arXiv preprint arXiv:2512.11222},
  year   = {2025}
}

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28 pages