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Well-Quasi Orders and Hierarchy Theory

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Book cover Well-Quasi Orders in Computation, Logic, Language and Reasoning

Part of the book series: Trends in Logic ((TREN,volume 53))

Abstract

We discuss some applications of WQOs to several fields were hierarchies and reducibilities are the principal classification tools, notably to Descriptive Set Theory, Computability theory and Automata Theory. While the classical hierarchies of sets usually degenerate to structures very close to ordinals, the extension of them to functions requires more complicated WQOs, and the same applies to reducibilities. We survey some results obtained so far and discuss open problems and possible research directions.

Supported by Russian Science Foundation, project 18-11-00100.

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Acknowledgements

I am grateful to Leibniz-Zentrum für Informatik for accepting and taking care of Dagstuhl Seminars 08271, 11411, 15392, 16031 which were important for promoting the topic of this paper.

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Selivanov, V. (2020). Well-Quasi Orders and Hierarchy Theory. In: Schuster, P., Seisenberger, M., Weiermann, A. (eds) Well-Quasi Orders in Computation, Logic, Language and Reasoning. Trends in Logic, vol 53. Springer, Cham. https://doi.org/10.1007/978-3-030-30229-0_10

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