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A note on highly connected and well-connected Ramsey theory

Volume 260 / 2023

Chris Lambie-Hanson Fundamenta Mathematicae 260 (2023), 181-197 MSC: Primary 03E02; Secondary 03E35, 05C63. DOI: 10.4064/fm141-9-2022 Published online: 26 September 2022

Abstract

We study a pair of weakenings of the classical partition relation $\nu \rightarrow (\mu )^2_\lambda $, recently introduced by Bergfalk–Hrušák–Shelah and Bergfalk, respectively. Given an edge-coloring of the complete graph on $\nu $-many vertices, these weakenings assert the existence of monochromatic subgraphs exhibiting high degrees of connectedness rather than the existence of complete monochromatic subgraphs asserted by the classical relations. As a result, versions of these weakenings can consistently hold at accessible cardinals where their classical analogues would necessarily fail. We prove some complementary positive and negative results indicating the effect of large cardinals, forcing axioms, and square principles on these partition relations. We also prove a consistency result indicating that a non-trivial instance of the stronger of these two partition relations can hold at the continuum.

Authors

  • Chris Lambie-HansonInstitute of Mathematics of the Czech Academy of Sciences
    Žitná 25
    115 67 Praha 1, Czech Republic
    e-mail

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