On Szymański theorem on hereditary normality of β ω

Sergei Logunov

Commentationes Mathematicae Universitatis Carolinae (2022)

  • Volume: 62 63, Issue: 4, page 507-512
  • ISSN: 0010-2628

Abstract

top
We discuss the following result of A. Szymański in “Retracts and non-normality points" (2012), Corollary 3.5.: If F is a closed subspace of ω * and the π -weight of F is countable, then every nonisolated point of F is a non-normality point of ω * . We obtain stronger results for all types of points, excluding the limits of countable discrete sets considered in “Some non-normal subspaces of the Čech–Stone compactification of a discrete space” (1980) by A. Błaszczyk and A. Szymański. Perhaps our proofs look “more natural in this area”.

How to cite

top

Logunov, Sergei. "On Szymański theorem on hereditary normality of $\beta \omega $." Commentationes Mathematicae Universitatis Carolinae 62 63.4 (2022): 507-512. <http://eudml.org/doc/299044>.

@article{Logunov2022,
abstract = {We discuss the following result of A. Szymański in “Retracts and non-normality points" (2012), Corollary 3.5.: If $F$ is a closed subspace of $\omega ^\{*\}$ and the $\pi $-weight of $F$ is countable, then every nonisolated point of $F$ is a non-normality point of $\omega ^\{*\}$. We obtain stronger results for all types of points, excluding the limits of countable discrete sets considered in “Some non-normal subspaces of the Čech–Stone compactification of a discrete space” (1980) by A. Błaszczyk and A. Szymański. Perhaps our proofs look “more natural in this area”.},
author = {Logunov, Sergei},
journal = {Commentationes Mathematicae Universitatis Carolinae},
keywords = {Čech–Stone compactification; non-normality point; butterfly-point; countable $\pi $-weight},
language = {eng},
number = {4},
pages = {507-512},
publisher = {Charles University in Prague, Faculty of Mathematics and Physics},
title = {On Szymański theorem on hereditary normality of $\beta \omega $},
url = {http://eudml.org/doc/299044},
volume = {62 63},
year = {2022},
}

TY - JOUR
AU - Logunov, Sergei
TI - On Szymański theorem on hereditary normality of $\beta \omega $
JO - Commentationes Mathematicae Universitatis Carolinae
PY - 2022
PB - Charles University in Prague, Faculty of Mathematics and Physics
VL - 62 63
IS - 4
SP - 507
EP - 512
AB - We discuss the following result of A. Szymański in “Retracts and non-normality points" (2012), Corollary 3.5.: If $F$ is a closed subspace of $\omega ^{*}$ and the $\pi $-weight of $F$ is countable, then every nonisolated point of $F$ is a non-normality point of $\omega ^{*}$. We obtain stronger results for all types of points, excluding the limits of countable discrete sets considered in “Some non-normal subspaces of the Čech–Stone compactification of a discrete space” (1980) by A. Błaszczyk and A. Szymański. Perhaps our proofs look “more natural in this area”.
LA - eng
KW - Čech–Stone compactification; non-normality point; butterfly-point; countable $\pi $-weight
UR - http://eudml.org/doc/299044
ER -

References

top
  1. Bešlagić A., van Douwen E. K., 10.1016/0166-8641(90)90110-N, Topology Appl. 35 (1990), no. 2–3, 253–260. MR1058805DOI10.1016/0166-8641(90)90110-N
  2. Błaszczyk A., Szymański A., Some non-normal subspaces of the Čech–Stone compactification of a discrete space, Abstracta, 8th Winter School on Abstract Analysis, Praha, Czechoslovak Academy of Sciences, 1980, 35–38. 
  3. Gryzlov A. A., On the question of hereditary normality of the space β ω ω , Topology and Set Theory Udmurt. Gos. Univ. Izhevsk (1982), 61–64 (Russian). MR0760274
  4. Logunov S., On non-normality points and metrizable crowded spaces, Comment. Math. Univ. Carolin. 48 (2007), no. 3, 523–527. MR2374131
  5. Rajagopalan M., β N - N - { p } is not normal, J. Indian Math. Soc. (N.S.) 36 (1972), 173–176. MR0321012
  6. Shapirovkij B., On embedding extremely disconnected spaces in compact Hausdorff spaces, b -points and weight of point-wise normal spaces, Dokl. Akad. Nauk SSSR 223 (1975), 1083–1086 (Russian). MR0394609
  7. Szymański A., Retracts and non-normality points, Topology Proc. 40 (2012), 195–201. MR2832067
  8. Warren N. M., Properties of Stone–Čech compactifications of discrete spaces, Proc. Amer. Math. Soc. 33 (1972), 599–606. MR0292035

NotesEmbed ?

top

You must be logged in to post comments.

To embed these notes on your page include the following JavaScript code on your page where you want the notes to appear.

Only the controls for the widget will be shown in your chosen language. Notes will be shown in their authored language.

Tells the widget how many notes to show per page. You can cycle through additional notes using the next and previous controls.

    
                

Note: Best practice suggests putting the JavaScript code just before the closing </body> tag.