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MATHEMATICS
On tightness and pseudocharacter of compact $T_1$-spaces
A. A. Gryzlov, R. A. Golovastov Udmurt State University, ul. Universitetskaya, 1, Izhevsk, 426034, Russia
Abstract:
We consider the relationship between the pseudocharacter $\psi(X)$ and the tightness $t(X)$ of compact $T_1$-spaces $X$. We prove that $t(X)\leqslant\psi(X)$ for self-adjoined $T_1$-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 $T_1$-spaces there is no relationship between these cardinal invariants.
We give an example of a compact $T_1$-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:
$T_1$-space, compact, tightness, pseudocharacter.
Received: 15.07.2019
Citation:
A. A. Gryzlov, R. A. Golovastov, “On tightness and pseudocharacter of compact $T_1$-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: | 353 | Full-text PDF : | 198 | References: | 42 |
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