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・ Erdős number
・ Erdős Prize
・ Erdős space
・ Erdősmecske
・ Erdősmárok
・ Erdős–Anning theorem
・ Erdős–Bacon number
・ Erdős–Borwein constant
・ Erdős–Burr conjecture
・ Erdős–Diophantine graph
・ Erdős–Faber–Lovász conjecture
・ Erdős–Fuchs theorem
・ Erdős–Gallai theorem
・ Erdős–Graham problem
・ Erdős–Gyárfás conjecture
Erdős–Hajnal conjecture
・ Erdős–Kac theorem
・ Erdős–Ko–Rado theorem
・ Erdős–Mordell inequality
・ Erdős–Nagy theorem
・ Erdős–Nicolas number
・ Erdős–Pósa theorem
・ Erdős–Rado theorem
・ Erdős–Rényi model
・ Erdős–Stone theorem
・ Erdős–Straus conjecture
・ Erdős–Szekeres theorem
・ Erdős–Szemerédi theorem
・ Erdős–Turán conjecture on additive bases
・ Erdős–Turán inequality


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Erdős–Hajnal conjecture : ウィキペディア英語版
Erdős–Hajnal conjecture

In graph theory, a branch of mathematics, the Erdős–Hajnal conjecture states that families of graphs defined by forbidden induced subgraphs have either large cliques or large independent sets.
More precisely, for an arbitrary undirected graph H, let \mathcal_H be the family of graphs that do not have H as an induced subgraph. Then, according to the conjecture, there exists a constant \delta_H > 0 such that the n-vertex graphs in \mathcal_H have either a clique or an independent set of size \Omega(n^).
In contrast, for random graphs in the Erdős–Rényi model with edge probability 1/2, both the maximum clique and the maximum independent set are much smaller: their size is proportional to the logarithm of n, rather than growing polynomially. Ramsey's theorem proves that no graph has both its maximum clique size and maximum independent set size smaller than logarithmic.
This conjecture is due to Paul Erdős and András Hajnal, who proved it to be true when H is a cograph. They also showed, for arbitrary ''H'', that the size of the largest clique or independent set grows superlogarithmically. As of 2014, however, the full conjecture has not been proven, and remains an open problem.
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