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Research notes on every problem, and a library of the papers behind them. Built from the open erdos repository.

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Claim. Theorem 1 of N. Alon, M. Bucić and B. Sudakov, Large cliques and independent sets all over the place, Proc. Amer. Math. Soc. 149 (2021), no. 8, 3145--3157, first posted as arXiv:2004.04718 on 2020-04-09, gives for every large nn an nn-vertex graph GG with mG(log⁡n)≤22(log⁡log⁡n)1/2+o(1)m_G(\log n)\le2^{2^{(\log\log n)^{1/2+o(1)}}}. The corpus states it on its result page. Here mG(k)m_G(k) is the least mm such that every set of at least mm vertices contains both a clique and an independent set of size at least kk, and logarithms are to base 22. Theorem 2 gives the explicit bound log⁡log⁡mG(k)≤6log⁡log⁡n log⁡log⁡k\log\log m_G(k)\le6\sqrt{\log\log n\,\log\log k} for n≥4n\ge4 and k≥log⁡nk\ge\log n. Since log⁡2n>ln⁡n\log_2n>\ln n, the same graph serves with natural logarithms. So the answer to Problem 805 is yes for every g(n)<ng(n)<n with g(n)≥mG(log⁡n)g(n)\ge m_G(\log n).

Covers. The instances with $2^{2^{(\log\log n)^{1/2+\varepsilon}}}\le g(n)<n$ for a fixed ε>0\varepsilon>0 and all large nn, answered yes. Not covered: every smaller gg. The bound exceeds every fixed power of log⁡n\log n, so g(n)=(log⁡n)3g(n)=(\log n)^3 stays open, as the paper says.

Depends on. Nothing in this wiki; the construction is the paper's own.

Acceptance. refereed: Proc. Amer. Math. Soc. 149 (2021), no. 8, 3145--3157, published online 14 May 2021. The site's curator, T. F. Bloom, credits the construction in the problem's commentary. The site labels the problem OPEN, so that commentary is not acceptance, and no reviewed is listed. Source card: Alon, Bucić and Sudakov.