We recall that, in a topological space, a point is said to be an interior point of a subset if the latter is a neighborhood of the point in question. The set of interior points of a subset is called the interior of this subset. It is well-known that a subset is open if and … Lire la suite de A characterization of the existence of an interior point
Topological space
An exercise on a characterization of the existence of an interior point
We recall that, in a topological space, a point is said to be an interior point of a subset if the latter is a neighborhood of the point in question. The set of interior points of a subset is called the interior of this subset. It is well-known that a subset is open if and … Lire la suite de An exercise on a characterization of the existence of an interior point
Topologies from interior operators
As seen in a preceding entry of this blog, topologies on a set can be defined by the means of closure operators. In this note, we prove that topologies can also be constructed using interior operators. In fact, the note is a solution of an exercise formulated previously. We repeat the statement of the exercise … Lire la suite de Topologies from interior operators
An exercise on topologies from interior operators
In a preceding entry of this blog, we saw that topologies arise from closure operators. This note raises the question of whether this is also valid for interior operators. The question is framed precisely in the exercise below. To approach the issue with serenity, it should be remembered here that closure and interior are dual … Lire la suite de An exercise on topologies from interior operators
Topologies from closure operators
Topologies on a set can be defined by the means of neighborhood systems. In this note, we prove that topologies can also be constructed using closure operators. In fact, the note is a solution of an exercise formulated in a previous entry of this blog. We repeat the statement of the exercise in question here, … Lire la suite de Topologies from closure operators
An exercise on topologies from closure operators
It is well-known that a topology on a set can be defined by the means of a neighborhood system. Topologies can also arise from certain operators. In this note, we set an exercise, which invites to prove that topologies can be obtained from closure operators. The exercise statement below provides a clear definition of closure … Lire la suite de An exercise on topologies from closure operators
The characteristic function and the Sierpinski-space
A topological space, whose underlying set has two elements, is called the Sierpinski-space if its topology is non-discrete and non-indiscrete. In this publication, we give a necessary and sufficient condition for the continuity of a characteristic function from a topological space into the Sierpinski-space. In fact, this is our solution to an exercise outlined in … Lire la suite de The characteristic function and the Sierpinski-space
An exercise on the characteristic function and the Sierpinski-space
The characteristic function appears in many fields of mathematics. This publication set an exercise that allows to discover elementary features of the characteristic function in the context of Set Theory and General Topology. The exercise also introduces the Sierpinski-space. In a preceding entry of this blog, we established that there exactly four topologies on a … Lire la suite de An exercise on the characteristic function and the Sierpinski-space
Formalis Mathematica 