English

The Gamified Kat\v{e}tov order is not linear (in fact, very much not so)

Logic 2026-05-21 v1 Category Theory

Abstract

Recently, the authors introduced the Gamified Kat\v{e}tov order on filters over ω\omega. This was shown to be strictly coarser than the classical Kat\v{e}tov order, and in fact collapses all MAD families to a single equivalence class. In the opposite direction, the present paper shows that the Gamified Kat\v{e}tov order also embeds P(ω)/Fin\mathcal{P}(\omega)/\mathrm{Fin}, and thus contains an antichain of size continuum. The analysis brings into focus some interesting connections with Ramsey theory. As part of a broader programme investigating the interplay between combinatorial and computable complexity, we then apply our construction to produce a large new family of non-modest degrees in the extended Weihrauch hierarchy, which arise from associated effective subtoposes.

Keywords

Cite

@article{arxiv.2605.21473,
  title  = {The Gamified Kat\v{e}tov order is not linear (in fact, very much not so)},
  author = {Takayuki Kihara and Ming Ng},
  journal= {arXiv preprint arXiv:2605.21473},
  year   = {2026}
}

Comments

28 pages, 1 figure