Abstract
A topological space is called paranormal if any countable discrete system of closed sets {Dn:n = 1, 2, 3,...} can be expanded to a locally finite system of open sets {Un:n = 1, 2, 3,...}, i.e., Dn is contained in Un for all n, and Dm ∩ Un≠ Ø if and only if Dm = Dn. It is proved that if X is a countably compact space whose cube is hereditarily paranormal, then X is metrizable.
References
A. P. Kombarov, “TheWeak Form of Normality,” Vestnik Mosk. Univ., Matem. Mekhan., No 5, 48 (2017) [Moscow Univ. Math. Bulletin 72 (5), 203 (2017)].
M. Katetov, “Complete Normality of Cartesian Products,” Fund. Math. 35, 271 (1948).
P. Zenor, “Countable Paracompactness in Product Spaces,” Proc. Amer. Math. Soc. 30, 199 (1971).
J. Chaber, “Conditions which Imply Compactness in Countably Compact Spaces,” Bull. Acad. Pol. Sci., Ser. Sci. Math. Astronom. et Phys. 24, 993 (1976).
R. Engelking, General Topology (PWN, Warsaw, 1977; Nauka, Moscow, 1986).
P. Nyikos, “Problem Section: Problem B,” Topol. Proc. 9, 367 (1984).
A. P. Kombarov, “On Σ-Products of Topological Spaces.” Doklady Akad. Nauk SSSR 199 (3), 526 (1971) [Soviet Math. Doklady 12, 1101 (1971)].
A. P. Kombarov, “On Expandable Discrete Collections,” Topol. and Appl. 69, 283 (1996).
A. P. Kombarov, “On a Theorem of A. H. Stone,” Doklady Akad. Nauk SSSR 270, 38 (1983) [Soviet Math. Doklady 27, 544 (1983)].
A. P. Kombarov, “Product of Normal Spaces. Uniformities on Σ-Products,” Doklady Akad. Nauk SSSR 205, 1033 (1972) [Soviet. Math. Doklady 13 (4), 1068 (1972)].
Author information
Authors and Affiliations
Corresponding author
Additional information
Original Russian Text © A.V. Bogomolov, 2018, published in Vestnik Moskovskogo Universiteta, Matematika. Mekhanika, 2018, Vol. 73, No. 4, pp. 54–56.
About this article
Cite this article
Bogomolov, A.V. The Paranormality of Products and Their Subsets. Moscow Univ. Math. Bull. 73, 156–157 (2018). https://doi.org/10.3103/S0027132218040058
Received:
Published:
Issue Date:
DOI: https://doi.org/10.3103/S0027132218040058