• Korean Journal of Mathematics
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• 제18권1호
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• pp.45-52
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• 2010

Generalizing $Lindel{\ddot{o}}f$ frames and almost compact frames, we introduce a concept of almost $Lindel{\ddot{o}}f$ frames. Using a concept of ${\delta}$-filters on frames, we characterize almost $Lindel{\ddot{o}}f$ frames and then have their permanence properties. We also show that almost $Lindel{\ddot{o}}f$ regular $D({\aleph}_1)$ frames are exactly $Lindel{\ddot{o}}f$ frames. Finally we construct an almost $Lindel{\ddot{o}}fication$ of a frame L via the simple extension of L associated with the set of all ${\delta}$-filters F on L with ${\bigvee}\{x^*{\mid}x{\in}F\}=e$.

• 충청수학회지
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• 제10권1호
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• pp.43-56
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• 1997

In this paper, we introduce a new class of ${\delta}$-frames and study its properties. To do so, we introduce ${\delta}$-filters, almost Lindel$\ddot{o}$f frames and Lindel$\ddot{o}$f frames. First, we show that a complete chain or a complete Boolean algebra is a ${\delta}$-frame. Next, we show that a ${\delta}$-frame L is almost Lindel$\ddot{o}$f iff for any ${\delta}$-filter F in L, ${\vee}\{x^*\;:\;x{\in}F\}{\neq}e$. Last, we show that every regular Lindelof ${\delta}$-frame is normal and a Lindel$\ddot{o}$f ${\delta}$-frame is preserved under a ${\delta}$-isomorphism which is dense and codense.

• Korean Journal of Mathematics
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• 제15권2호
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• pp.87-100
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• 2007

We introduce a concept of countably strong inclusions ${\triangleleft}$ and that of ${\triangleleft}-{\sigma}$-ideals and prove that the subframe $S({\triangleleft})$ of the frame ${\sigma}IdL$ of ${\sigma}$-ideals is a Lindel$\ddot{o}$fication of a frame L. We also deal with conditions for which the converse holds. We show that any countably approximating regular $D({\aleph}_1)$ frame has the smallest countably strong inclusion and any frame which has the smallest $D({\aleph}_1)$ Lindel$\ddot{o}$fication is countably approximating regular $D({\aleph}_1)$.

• Kyungpook Mathematical Journal
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• 제45권4호
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• pp.455-470
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• 2005

This paper introduces compactness notions for frames which are expressed in terms of the convergence of suitably specified general filters. It establishes several preservation properties for them as well as their coreflectiveness in the setting of regular frames. Further, it shows that supercompact, compact, and $Lindel{\ddot{o}}f$ frames can be described by compactness conditions of the present form so that various familiar facts become consequences of these general results. In addition, the Prime Ideal Theorem and the Axiom of Countable Choice are proved to be equivalent to certain conditions connected with the kind of compactness considered here.