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On the inducibility of oriented graphs on four vertices. (English) Zbl 1489.05075

Summary: We consider the problem of determining the inducibility (maximum possible asymptotic density of induced copies) of oriented graphs on four vertices. We provide exact values for more than half of the graphs, and very close lower and upper bounds for all the remaining ones. It occurs that, for some graphs, the structure of extremal constructions maximizing density of its induced copies is very sophisticated and complex.

MSC:

05C35 Extremal problems in graph theory
05C20 Directed graphs (digraphs), tournaments
05C60 Isomorphism problems in graph theory (reconstruction conjecture, etc.) and homomorphisms (subgraph embedding, etc.)
05C30 Enumeration in graph theory
90C22 Semidefinite programming

Software:

SageMath; Flagmatic; CSDP
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References:

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