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Co-intersection graphs of nonabelian finite simple groups have diameter two
Abstract
Let G be a finite group. The co-intersection graph ΔG c of G has as its vertices the nontrivial proper subgroups of G, with edges joining those pairs of subgroups which intersect trivially. It is clear that every connected component of ΔG c has diameter at most three. In this Note, we show that when T is a nonabelian finite simple group, ΔT is connected of diameter exactly two. We also make several observations about the extent to which a finite group is determined by its co-intersection graph, and about the class of finite graphs arising as co-intersection graphs.
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BibTeX
@misc{bradford2026cointersection,
title = {{Co-intersection graphs of nonabelian finite simple groups have diameter two}},
author = {Henry Bradford and Kamilla Rekvényi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.07948},
eprint = {2609.07948},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.07948},
}
RIS
TY - UNPB
TI - Co-intersection graphs of nonabelian finite simple groups have diameter two
AU - Henry Bradford
AU - Kamilla Rekvényi
PY - 2026
DA - 2026/09/07
PB - arXiv
DO - 10.48550/arxiv.2609.07948
UR - https://arxiv.org/abs/2609.07948
AB - Let G be a finite group. The co-intersection graph Δ_G ^c of G has as its vertices the nontrivial proper subgroups of G, with edges joining those pairs of subgroups which intersect trivially. It is clear that every connected component of Δ_G ^c has diameter at most three. In this Note, we show that when T is a nonabelian finite simple group, Δ_T is connected of diameter exactly two. We also make several observations about the extent to which a finite group is determined by its co-intersection graph, and about the class of finite graphs arising as co-intersection graphs.
ER -