I'm interested in general topology, order theory, and graph theory. This link takes you to my preprints on arXiv.

## Generalizing the T_0 separation axiom

The starting point of this blog post is a slight reformulation of the separation axiom: A topological space is if for all there is a set such that Given a cardinal , we say that a space is if for … Continue reading

## Basics on towers on the natural numbers

For we write if is finite, and we write if and . A tower is a collection of co-infinite subsets of such that for all we have and either or . ( is co-infinite if is infinite.) If are towers, … Continue reading

## A definition of minor (in graph theory)

Many people I talk to about graph theory feel some uneasiness when it comes to the notion of “minor”. I want to try to alleviate this feeling by providing the definiton of minor that I work with. First an easy … Continue reading

## Any graph or its complement is connected

This is a short note of something that I wasn’t sure whether it is true for infinite graphs. Let be any simple, undirected graph, finite or infinite, such that . By we denote the complement of . Proposition. At least … Continue reading

## Ode to ed (Unix standard text editor)

Encouraged by Eric S. Raymond’s book The Art of Unix Programming I have started using ed. My affection for it keeps growing. To begin with, it is the prime example of minimality, a property that is cherished all over the … Continue reading