English

Untranscendable order types

Combinatorics 2026-03-02 v1 Logic

Abstract

We introduce and study a multiplicative analogue of additive indecomposability for linear order types that we call untranscendability, as well as a strengthening that we call ss-untranscendability. We show that, with the unique exception of the two-point type, every untranscendable type is additively indecomposable, and every σ\sigma-scattered untranscendable type is strongly indecomposable. Under the Proper Forcing Axiom, every untranscendable Aronszajn type is strongly indecomposable. We also show that a theorem of Hagendorf and Jullien, that every strictly additively indecomposable type must be strictly indecomposable to either the left or right, has a natural analogue for ss-untranscendable types.

Keywords

Cite

@article{arxiv.2602.24285,
  title  = {Untranscendable order types},
  author = {Garrett Ervin and Alberto Marcone and Thilo Weinert},
  journal= {arXiv preprint arXiv:2602.24285},
  year   = {2026}
}
R2 v1 2026-07-01T10:56:04.032Z