Maximum vertices in a \(3\)-chromatic \(r\)-clique
Search
Subjects
- All (170)
- Ramsey Theory (40)
- Extremal Graph Theory (40)
- Coloring, Packing, and Covering (25)
- Random Graphs and Graph Enumeration (16)
- Hypergraphs (35)
- Infinite Graphs (14)
About Erdös
About This Site
A hypergraph \( H\) consists of a vertex set \( V\) together with a family \( E\) of subsets of \( V\), which are called the edges of \( H\). A \( r\)-uniform hypergraph, or \( r\)-graph, for short, is a hypergraph whose edge set consists of \( r\)-subsets of \( V\). A graph is just a special case of an \( r\)-graph with \( r=2\).
A hypergraph \( H\) is said to be \( k\)-chromatic if the vertices of \( H\) can be colored in \( k\) colors so that every edge has at least \( 2\) colors.
An \( r\)-graph is said to be a clique if every two edges have a nontrivial intersection. An unexpected fact about \( 3\)-chromatic \( r\)-graphs is that there are only finitely many \( 3\)-chromatic \( r\)-cliques.
A problem on maximum \(3\)-chromatic hypergraphs (proposed by Erdös and Lovász [1])
Determine the maximum number \(N(r)\) of vertices a \(3\)-chromatic \(r\)-clique can have.In [1], it was shown that
Bibliography | |
---|---|
1 |
P. Erdös and L. Lovász, Problems and results on 3-chromatic
hypergraphs and some related questions,
Infinite and finite sets (Colloq., Keszthely,
1973; dedicated to P. Erdös on his 60th birthday), Vol. I; Colloq.
Math. Soc. János Bolyai, Vol. 10, 609-627, North-Holland,
Amsterdam, 1975.
|
2 | Zs. Tuza. Critical hypergraphs and intersecting set-pair systems. J. Comb. Theory B 39 (1985), 134-145.
|