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PreprintarXiv licencearXiv

Intersections of Oriented Graphs and Tournaments

Abstract

Given two tournaments of order n, Bollobás and Scott defined their discrepancy as the largest deviation of their overlap from its random average under relabelling, and they asked whether the resulting discrepancy is always Ω(n3/2). We answer this question by proving that there is an absolute constant c>0 such that every pair of tournaments T,U of order n has discrepancy at least cn3/2. More generally, if D and H are oriented graphs of order n with e(D) = p binomn2 and e(H) = q binomn2 satisfying 16/n ≤ p, q ≤ 1 − 16/n, then there is an absolute constant c > 0 such that their discrepancy is at least c(p(1−p)q(1−q))3n3/2. We also show that these two-graph estimates extend to intersections of any fixed number of graphs, tournaments, and oriented graphs.

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BibTeX
@misc{yang2026intersections,
  title = {{Intersections of Oriented Graphs and Tournaments}},
  author = {Zhanping Yang and Qinghou Zeng},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2608.27965},
  eprint = {2608.27965},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.27965},
}
RIS
TY  - UNPB
TI  - Intersections of Oriented Graphs and Tournaments
AU  - Zhanping Yang
AU  - Qinghou Zeng
PY  - 2026
DA  - 2026/09/07
PB  - arXiv
DO  - 10.48550/arxiv.2608.27965
UR  - https://arxiv.org/abs/2608.27965
AB  - Given two tournaments of order n, Bollobás and Scott defined their discrepancy as the largest deviation of their overlap from its random average under relabelling, and they asked whether the resulting discrepancy is always Ω(n^3/2). We answer this question by proving that there is an absolute constant c>0 such that every pair of tournaments T,U of order n has discrepancy at least cn^3/2. More generally, if D and H are oriented graphs of order n with e(D) = p binomn2 and e(H) = q binomn2 satisfying 16/n ≤ p, q ≤ 1 − 16/n, then there is an absolute constant c > 0 such that their discrepancy is at least c(p(1−p)q(1−q))^3n^3/2. We also show that these two-graph estimates extend to intersections of any fixed number of graphs, tournaments, and oriented graphs.
ER  -