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MATHEMATICS
On tightness and pseudocharacter of compact T1-spaces
A. A. Gryzlov, R. A. Golovastov Udmurt State University, ul. Universitetskaya, 1, Izhevsk, 426034, Russia
Abstract:
We consider the relationship between the pseudocharacter ψ(X) and the tightness t(X) of compact T1-spaces X. We prove that t(X)⩽ψ(X) for self-adjoined T1-spaces, i.e., the spaces where a subset is closed if and only if it is compact. We also show that in general for compact T1-spaces there is no relationship between these cardinal invariants.
We give an example of a compact T1-space such that the tightness of this space is uncountable, but its pseudocharacter is countable. Another example shows the space X
whose tightness is countable, but its pseudocharacter is uncountable.
Keywords:
T1-space, compact, tightness, pseudocharacter.
Received: 15.07.2019
Citation:
A. A. Gryzlov, R. A. Golovastov, “On tightness and pseudocharacter of compact T1-spaces”, Vestn. Udmurtsk. Univ. Mat. Mekh. Komp. Nauki, 29:3 (2019), 312–318
Linking options:
https://www.mathnet.ru/eng/vuu684 https://www.mathnet.ru/eng/vuu/v29/i3/p312
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Abstract page: | 387 | Full-text PDF : | 216 | References: | 51 |
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