Abstract
The classical extremal problem is that of computing the maximum number of edges in an F-free graph. In particular, Turán’s theorem entirely resolves the case where \(F=K_{r+1}\). Later results, known as supersaturation theorems, proved that in a graph containing more edges than the extremal number, there must also be many copies of \(K_{r+1}\). Alon and Shikhelman introduced a broader class of extremal problems, asking for the maximum number of copies of a graph T in an F-free graph (so that \(T=K_2\) is the classical extremal number). In this paper we determine some of these generalized extremal numbers when T and F are stars or cliques and prove some supersaturation results for them.
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Alon, N., Shikhelman, C.: Many \(T\) copies in \(H\)-free graphs. J. Combin. Theory Ser. B 121, 146–172 (2016)
Bollobás, B.: On complete subgraphs of different orders. Math. Proc. Camb. Philos. Soc. 79(1), 19–24 (1976)
Bollobás, B., Nikiforov, V.: Degree powers in graphs with forbidden subgraphs. Electron. J. Combin. 11(1), 8 (2004). Research Paper 42. http://www.combinatorics.org/Volume_11/Abstracts/v11i1r42.html
Caro, Y., Yuster, R.: A Turán type problem concerning the powers of the degrees of a graph. Electron. J. Combin. 7, 14 (2000). Research Paper 47. http://www.combinatorics.org/Volume_7/Abstracts/v7i1r47.html
Chase, Z.: The maximum number of triangles in a graph of given maximum degree. Adv. Comb. 10, 5 (2020). https://doi.org/10.19086/aic.16788
Engbers, J., Galvin, D.: Counting independent sets of a fixed size in graphs with a given minimum degree. J. Graph Theory 76(2), 149–168 (2014). https://doi.org/10.1002/jgt.21756
Erdős, P.: Some theorems on graphs. Riveon Lematematika 9, 13–17 (1955)
Erdős, P.: On a theorem of Rademacher–Turán. Ill. J. Math. 6, 122–127 (1962). http://projecteuclid.org/euclid.ijm/1255631811
Erdős, P.: On the number of complete subgraphs contained in certain graphs. Magyar Tud. Akad. Mat. Kutató Int. Közl. 7, 459–464 (1962)
Erdős, P.: Extremal problems in graph theory. In: Theory of Graphs and its Applications (Proc. Sympos. Smolenice, 1963), pp. 29–36. Publ. House Czechoslovak Acad. Sci., Prague (1964)
Erdős, P., Stone, A.H.: On the structure of linear graphs. Bull. Am. Math. Soc. 52, 1087–1091 (1946)
Füredi, Z.: New asymptotics for bipartite Turán numbers. J. Combin. Theory Ser. A 75(1), 141–144 (1996)
Gan, W., Loh, P.S., Sudakov, B.: Maximizing the number of independent sets of a fixed size. Combin. Probab. Comput. 24(3), 521–527 (2015). https://doi.org/10.1017/S0963548314000546
Gerbner, D., Patkós, B.: Generalized Turán problems for complete bipartite graphs (2021) (under review)
Győri, E., Salia, N., Tompkins, C., Zamora, O.: The maximum number of \(P_\ell\) copies in \(P_k\)-free graphs. Acta Math. Univ. Comenian. (N.S.) 88(3), 773–778 (2019)
Györi, E., Pach, J., Simonovits, M.: On the maximal number of certain subgraphs in \(k_r\)-free graphs. Graphs Comb. 7(1), 31–37 (1991). https://doi.org/10.1007/BF01789461
Halfpap, A., Palmer, C.: On supersaturation and stability for generalized Turán problems. J Graph Theor. 97(2), 232–240 (2021). https://doi.org/10.1002/jgt.22652
Lidický, B., Murphy, K.: Maximizing five-cycles in \(k_r\)-free graphs. Eur J Combin. (2021). https://doi.org/10.1016/j.ejc.2021.103367
Lovász, L.: Combinatorial Problems and Exercises, 2nd edn. AMS Chelsea Publishing, Providence (2007). https://doi.org/10.1090/chel/361
Lovász, L., Simonovits, M.: On the number of complete subgraphs of a graph, pp. 431–441. Congressus Numerantium, No. XV (1976)
Lovász, L., Simonovits, M.: On the number of complete subgraphs of a graph. II. In: Studies in Pure Mathematics, pp. 459–495. Basel, Birkhäuser (1983)
Luo, R.: The maximum number of cliques in graphs without long cycles. J. Combin. Theory Ser. B 128, 219–226 (2018). https://doi.org/10.1016/j.jctb.2017.08.005
Moon, J.W., Moser, L.: On a problem of Turán. Magyar Tud. Akad. Mat. Kutató Int. Közl. 7, 283–286 (1962)
Nikiforov, V.: Graphs with many \(r\)-cliques have large complete \(r\)-partite subgraphs. Bull. Lond. Math. Soc. 40(1), 23–25 (2008)
Nikiforov, V.: The number of cliques in graphs of given order and size. Trans. Am. Math. Soc. 363(3), 1599–1618 (2011). https://doi.org/10.1090/S0002-9947-2010-05189-X
Pikhurko, O., Yilma, Z.B.: Supersaturation problem for color-critical graphs. J. Combin. Theory Ser. B 123, 148–185 (2017). https://doi.org/10.1016/j.jctb.2016.12.001
Rademacher, H.: unpublished (1941)
Razborov, A.A.: On the minimal density of triangles in graphs. Combin. Probab. Comput. 17(4), 603–618 (2008). https://doi.org/10.1017/S0963548308009085
Reiher, C.: The clique density theorem. Ann. Math. (2) 184(3), 683–707 (2016). https://doi.org/10.4007/annals.2016.184.3.1
Turán, P.: Eine Extremalaufgabe aus der Graphentheorie. Mat. Fiz. Lapok 48, 436–452 (1941)
Wood, D.R.: On the maximum number of cliques in a graph. Graphs Combin. 23(3), 337–352 (2007). https://doi.org/10.1007/s00373-007-0738-8
Zykov, A.A.: On some properties of linear complexes. Mat Sbornik N S 24(66), 163–188 (1949)
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The first author is supported in part by the Simons Foundation under Grant no. 524435. The third author is supported in part by the Simons Foundation under Grant no. 429383.
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Supported in part by the Simons Foundation under Grant no. 524435. Supported in part by the Simons Foundation under Grant no. 429383.
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Cutler, J., Nir, J. & Radcliffe, A.J. Supersaturation for Subgraph Counts. Graphs and Combinatorics 38, 65 (2022). https://doi.org/10.1007/s00373-021-02454-y
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DOI: https://doi.org/10.1007/s00373-021-02454-y