拉姆齐定理是ω-自动的吗?
Is Ramsey's theorem omega-automatic?
摘要:
研究了Ω-自动(超)图中无限团的存在性。事实证明,这种情况比一般的不可数图要好得多,但不如自动图好。更具体地说,我们证明了每一个不可数的欧米茄自动图包含一个不可数的co-context-free集团或anticlique,但不一定是一个上下文无关(更不用说定期)集团或anticlique。我们还证明了不可数的Ω-自动三元超图根本不需要有不可数的团或反团。
英文摘要:
We study the existence of infinite cliques in omega-automatic (hyper-)graphs. It turns out that the situation is much nicer than in general uncountable graphs, but not as nice as for automatic graphs. More specifically, we show that every uncountable omega-automatic graph contains an uncountable co-context-free clique or anticlique, but not necessarily a context-free (let alone regular) clique or anticlique. We also show that uncountable omega-automatic ternary hypergraphs need not have uncountable cliques or anticliques at all.
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