English

Semi-inducibility of 4-vertex graphs

Combinatorics 2026-05-28 v2

Abstract

For a graph HH whose edges are coloured blue or red, the HH-semi-inducibility problem asks for the maximum, over all graphs GG of given order nn, of the number of injections from the vertex set of HH into the vertex set of GG that send red (resp. blue) edges of HH to edges (resp. non-edges) of GG. We consider all possible 4-vertex non-complete graphs HH and essentially resolve all remaining cases except when HH is the 3-edge path coloured blue-blue-red in this order (or is equivalent to this case). Some of our proofs are computer-generated, using the flag algebra method of Razborov.

Keywords

Cite

@article{arxiv.2510.24336,
  title  = {Semi-inducibility of 4-vertex graphs},
  author = {Levente Bodnár and Oleg Pikhurko},
  journal= {arXiv preprint arXiv:2510.24336},
  year   = {2026}
}

Comments

34 pages