Session 27. Probabilistic and Extremal Combinatorics

Counting \(H\)-free graphs

Wojciech Samotij, Tel Aviv University, Israel
In this talk, we shall survey a large body of enumerative results in the context of \(H\)-free graphs, that is, graphs not containing a copy of a fixed graph \(H\) as a subgraph. In particular, we shall show how the recent ``hypergraph containers'' theorem of Balogh, Morris, and the speaker, proved independently by Saxton and Thomason, allows one to derive (for each \(H\)) an approximate structural description of a typical (random) \(H\)-free graph with a given number of vertices and edges. In several interesting cases, such as when \(H\) is a clique, these approximate structural descriptions may be made precise. We shall also mention several challenging open questions.
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