English

Strongly regular graphs with parameters (81,30,9,12) and a new partial geometry pg(5,5,2)

Combinatorics 2020-10-02 v2

Abstract

Twelve new strongly regular graphs with parameters (81,30,9,12) are found as graphs invariant under certain subgroups of the automorphism groups of the two previously known graphs that arise from 2-weight codes. One of these new graphs is geometric and yields a partial geometry with parameters pg(5,5,2) that is not isomorphic to the partial geometry discovered by J. H. van Lint and A. Schrijver in 1981.

Keywords

Cite

@article{arxiv.2009.09544,
  title  = {Strongly regular graphs with parameters (81,30,9,12) and a new partial geometry pg(5,5,2)},
  author = {Dean Crnković and Andrea Švob and Vladimir D. Tonchev},
  journal= {arXiv preprint arXiv:2009.09544},
  year   = {2020}
}

Comments

11 pages

R2 v1 2026-06-23T18:40:32.625Z