• Communications of the Korean Mathematical Society
• /
• v.24 no.4
• /
• pp.595-603
• /
• 2009

We obtain some characterizations of continuous, open and closed functions in intuitionistic topological spaces. Moreover we reveal that the category of topological spaces is a bireflective full subcategory of the category of intuitionistic topological spaces.

• Journal of applied mathematics & informatics
• /
• v.42 no.3
• /
• pp.471-481
• /
• 2024

In this paper, the concept of D-sets will be applied to create D-lindelöf spaces, a new type of topological space covering the property. This is performed by using a D-cover, which is a special type of cover. The primary purpose of this work is to introduce the principles and concepts of D-lindelöf spaces. We look into their properties as well as their relationships with other topological spaces. The basic relationship between D-lindelöf spaces and lindelöf spaces, as well as many other topological spaces, will be given and described, including D-compact, D-countably compact, and D-countably lindelöf spaces. Many novel theories, facts, and illustrative and counter-examples will be investigated. We will use several informative instances to explore certain of the features of the Cartesian product procedure across D-lindelöf spaces as well as additional spaces under more conditions.

• Bulletin of the Korean Mathematical Society
• /
• v.20 no.2
• /
• pp.95-97
• /
• 1983

In this paper, we show a necessary and sufficient condition for QHC spaces to be S-closed. T. Thomson introduced S-closed spaces in [2]. A topological space X is said to be S-closed if every semi-open cover of X admits a finite subfamily such that the closures of whose members cover the space, where a set A is semi-open if and only if there exists an open set U such that U.contnd.A.contnd.Cl U. A topological space X is quasi-H-closed (denote QHC) if every open cover has a finite subfamily whose closures cover the space. If a topological space X is Hausdorff and QHC, then X is H-closed. It is obvious that every S-closed space is QHC but the converse is not true [2]. In [1], Cameron proved that an extremally disconnected QHC space is S-closed. But S-closed spaces are not necessarily extremally disconnected. Therefore we want to find a necessary and sufficient condition for QHC spaces to be S-closed. A topological space X is said to be semi-locally S-closed if each point of X has a S-closed open neighborhood. Of course, a locally S-closed space is semi-locally S-closed.

• Journal of the Chungcheong Mathematical Society
• /
• v.34 no.3
• /
• pp.259-269
• /
• 2021

We shall study the following. Let 𝜙 be an expansive flow on a compact TVS-cone metric space (X, d). First, we give some equivalent ways of defining expansiveness. Second, we show that expansiveness is conjugate invariance. Finally, we prove that lim sup ${\frac{1}{t}}$ log v(t) ≤ h(𝜙), where v(t) denotes the number of closed orbits of 𝜙 with a period 𝜏 ∈ [0, t] and h(𝜙) denotes the topological entropy. Remark that in 1972, R. Bowen and P. Walters had proved this three statements for an expansive flow on a compact metric space [?].

• Korean Journal of Mathematics
• /
• v.29 no.3
• /
• pp.493-499
• /
• 2021

Every closed subset of a compact topological space is compact. Also every compact subset of a Hausdorff topological space is closed. It follows that compact subsets are precisely the closed subsets in a compact Hausdorff space. It is also proved that a topological space is maximal compact if and only if its compact subsets are precisely the closed subsets. A locale is a categorical extension of topological spaces and a frame is an object in its opposite category. We investigate to find whether the closed sublocales are exactly the compact sublocales of a compact Hausdorff frame. We also try to investigate whether the closed sublocales are exactly the compact sublocales of a maximal compact frame.

• The Mathematical Education
• /
• v.13 no.2
• /
• pp.29-31
• /
• 1974

P.Zenor에 의해서 Monotonically Normal space가 정의되었으며 그후 R. Health와 D. Lutzer에 의해서 Linearly ordered topological space가 Monotonically Normal 임을 증명했다. 한편 Zenor는 Monotonically Normal Space의 hereditary에 관한 것을 question으로 남겼는데 Health와 Lutzer가 증명했고 또 그 증명보다 더 간단한 증명을 Calos R. Boyers가 증명했다[3]. 뿐만 아니라 그 결과로서 Linearly ordered topological space와 Elastic space 가 Monotonically Normal space임을 밝혔다. 또 [4]에서 Gary Gruenhage가 Monotonically Normal space가 Elastic space가 안됨을 counterexample을 들어서 증명했다. 결론적으로 Monotonically Normal spare와 Elastic space는 완전히 분리되었다. 또 Elastic space의 closed continuous image는 paracompact이고 Monotonically Normal 임을 증명했다. 이 논문에서는 본인이 밝힌 것은 Monotonically Normal space의 closed continuous image가 Mono tonically Normal임을 밝혔다.

• Honam Mathematical Journal
• /
• v.26 no.1
• /
• pp.77-83
• /
• 2004

A class of topological algebras, which we call it a fundamental one, has already been introduced generalizing the famous Cohen factorization theorem to more general topological algebras. To prove the generalized versions of Cohen's theorem to locally multilplicatively convex algebras, and finally to fundamental topological algebras, the completness of the background spaces is one of the main conditions. The local convexity of the completion of a locally convex space is a well known fact and here we have a discussion on the completness of fundamental metrizable topological vector spaces.

• Bulletin of the Korean Mathematical Society
• /
• v.24 no.1
• /
• pp.19-22
• /
• 1987

• Journal for History of Mathematics
• /
• v.14 no.2
• /
• pp.13-20
• /
• 2001

The topological structure of a topological space is completely determined by the data of convergence of filters on the space. We study the origin of convergence structure in the setting of filters and nets and their ramifications.

• Bulletin of the Korean Mathematical Society
• /
• v.61 no.1
• /
• pp.247-262
• /
• 2024

In this paper we introduce and study the notions of topological sensitivity and its stronger forms on semiflows and on product semiflows. We give a relationship between multi-topological sensitivity and thick topological sensitivity on semiflows. We prove that for a Urysohn space X, a syndetically transitive semiflow (T, X, 𝜋) having a point of proper compact orbit is syndetic topologically sensitive. Moreover, it is proved that for a T₃ space X, a transitive, nonminimal semiflow (T, X, 𝜋) having a dense set of almost periodic points is syndetic topologically sensitive. Also, wherever necessary examples/counterexamples are given.