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.
@InProceedings{kuske:LIPIcs.STACS.2010.2483, author = {Kuske, Dietrich}, title = {{Is Ramsey's Theorem omega-automatic?}}, booktitle = {27th International Symposium on Theoretical Aspects of Computer Science}, pages = {537--548}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-939897-16-3}, ISSN = {1868-8969}, year = {2010}, volume = {5}, editor = {Marion, Jean-Yves and Schwentick, Thomas}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2010.2483}, URN = {urn:nbn:de:0030-drops-24838}, doi = {10.4230/LIPIcs.STACS.2010.2483}, annote = {Keywords: Logic in computer science, automata, Ramsey theory} }
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