The number of cliques in graphs of given order and size

Let kr (n, m) denote the minimum number of r-cliques in graphs with n vertices and m edges. We give a lower bound on kr (n, m) that approximates kr (n, m) with an error smaller than n r / n 2 − 2m � . This essentially solves a sixty year old problem. The solution is based on a constraint minimization of certain multilinear forms. In our proof, a combinatorial strategy is coupled with extensive analytical arguments.

[1]  László Lovász,et al.  Very large graphs , 2009, 0902.0132.

[2]  Béla Bollobás,et al.  Modern Graph Theory , 2002, Graduate Texts in Mathematics.

[3]  R. A. R. A Z B O R O V On the minimal density of triangles in graphs , 2008 .

[4]  Paul Erdös,et al.  On a theorem of Rademacher-Turán , 1962 .

[5]  David C. Fisher Lower bounds on the number of triangles in a graph , 1989, J. Graph Theory.

[6]  Alexander A. Razborov,et al.  On the Minimal Density of Triangles in Graphs , 2008, Combinatorics, Probability and Computing.

[7]  B. Bollobás On complete subgraphs of different orders , 1976, Mathematical Proceedings of the Cambridge Philosophical Society.

[8]  V. Sós,et al.  Counting Graph Homomorphisms , 2006 .

[9]  M. Simonovits,et al.  On the number of complete subgraphs of a graph II , 1983 .

[10]  B. Bollobás,et al.  Extremal Graph Theory , 2013 .

[11]  Pál Erdös On the number of complete subgraphs and circuits contained in graphs , 1969 .

[12]  Alexander A. Razborov,et al.  Flag algebras , 2007, Journal of Symbolic Logic.

[13]  P. Erdös On an extremal problem in graph theory , 1970 .