91直播

91直播：马杰 教授（中国科学技术大学）

时间：2025年04月24日 10:30-

地点：理科楼LA103

摘要：Many fundamental problems in extremal combinatorics are equivalent to proving certain polynomial inequalities in graph homomorphism densities. In 2011, a breakthrough result by Hatami and Norine showed that it is undecidable to verify polynomial inequalities in graph homomorphism densities. Recently, Blekherman, Raymond and Wei extended this result by showing that it is also undecidable to determine the validity of polynomial inequalities in homomorphism densities for weighted graphs with edge weights taking real values. These two results resolved a question of Lovasz. In this talk, we consider the problem of determining the validity of polynomial inequalities in digraph homomorphism densities for tournaments. We prove that the answer to this problem is also undecidable. Joint work with Hao Chen, Yupeng Lin and Fan Wei.

邀请人: 傅士硕

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