English

On cardinal sequences of length < omega3

Logic 2018-10-29 v1

Abstract

We prove the following consistency result for cardinal sequences of length <\om3< \om_3: if GCH holds and \la\om2\la \geq \om_2 is a regular cardinal, then in some cardinal-preserving generic extension 2\om=\la2^{\om} = \la and for every ordinal η<\om3\eta < \om_3 and every sequence f=\ka\al:\al<ηf = \langle \ka_{\al} : \al < \eta \rangle of infinite cardinals with \ka\al\la\ka_{\al}\leq \la for \al<η\al < \eta and \ka\al=\om\ka_{\al} = \om if \mboxcf(\al)=\om2\mbox{cf}(\al) = \om_2, we have that ff is the cardinal sequence of some LCS space. Also, we prove that for every specific uncountable cardinal λ\lambda it is relatively consistent with ZFC that for every \al,\be<\om3\al,\be < \om_3 with \mboxcf(\al)<\om2\mbox{cf}(\al) < \om_2 there is an LCS space ZZ such that \mboxCS(Z)=ωα\concatλβ\mbox{CS}(Z) = \langle \omega \rangle_{\alpha}\concat \langle \lambda \rangle_{\beta}.

Cite

@article{arxiv.1810.11052,
  title  = {On cardinal sequences of length < omega3},
  author = {Juan Carlos Martínez and Lajos Soukup},
  journal= {arXiv preprint arXiv:1810.11052},
  year   = {2018}
}
R2 v1 2026-06-23T04:53:01.193Z