English

Simutaneously vanishing higher derived limits without large cardinals

Logic 2021-02-15 v1 Algebraic Topology

Abstract

A question dating to Sibe Marde\v{s}i\'{c} and Andrei Prasolov's 1988 work Strong homology is not additive, and motivating a considerable amount of set theoretic work in the ensuing years, is that of whether it is consistent with the ZFC axioms for the higher derived limits limn\mathrm{lim}^n (n>0)(n>0) of a certain inverse system A\mathbf{A} indexed by ωω{^\omega}\omega to simultaneously vanish. An equivalent formulation of this question is that of whether it is consistent for all nn-coherent families of functions indexed by ωω{^\omega}\omega to be trivial. In this paper, we prove that, in any forcing extension given by adjoining ω\beth_\omega-many Cohen reals, limnA\mathrm{lim}^n \mathbf{A} vanishes for all n>0n > 0. Our proof involves a detailed combinatorial analysis of the forcing extension and repeated applications of higher dimensional Δ\Delta-system lemmas. This work removes all large cardinal hypotheses from the main result of arXiv:1907.11744 and substantially reduces the least value of the continuum known to be compatible with the simultaneous vanishing of limnA\mathrm{lim}^n \mathbf{A} for all n>0n > 0.

Keywords

Cite

@article{arxiv.2102.06699,
  title  = {Simutaneously vanishing higher derived limits without large cardinals},
  author = {Jeffrey Bergfalk and Michael Hrušák and Chris Lambie-Hanson},
  journal= {arXiv preprint arXiv:2102.06699},
  year   = {2021}
}

Comments

30 pages, 1 figure

R2 v1 2026-06-23T23:06:55.805Z