English

Two results on cardinal invariants at uncountable cardinals

Logic 2018-01-30 v1

Abstract

We prove two ZFC theorems about cardinal invariants above the continuum which are in sharp contrast to well-known facts about these same invariants at the continuum. It is shown that for an uncountable regular cardinal κ\kappa, b(κ)=κ+\mathfrak{b}(\kappa) = {\kappa}^{+} implies a(κ)=κ+\mathfrak{a}(\kappa) = {\kappa}^{+}. This improves an earlier result of Blass, Hyttinen, and Zhang. It is also shown that if κω\kappa \geq {\beth}_{\omega} is an uncountable regular cardinal, then d(κ)r(κ)\mathfrak{d}(\kappa) \leq \mathfrak{r}(\kappa). This result partially dualizes an earlier theorem of the authors.

Keywords

Cite

@article{arxiv.1801.09369,
  title  = {Two results on cardinal invariants at uncountable cardinals},
  author = {Dilip Raghavan and Saharon Shelah},
  journal= {arXiv preprint arXiv:1801.09369},
  year   = {2018}
}

Comments

8 pages. Submitted