Header Image

Tarski's automorphsisms

November 14, 2024
I first came across Albert Lautman (nLab) after reading Fernando Zalamea’s remarks on his importance to structural mathematics in Synthetic philosophy of contemporary mathematics. While reading …

Sheaves are presheaves with an equalizer diagram

October 26, 2024
A sheaf on a topological space $ X $ can be defined as a presheaf $ F: \text{Open}(X)^{\text{op}} \to \mathbf{Set} $ such that for any open covering $ { U_i } $ $ (i \in I) $ of an open set $ U $, the …

Free semimodules and their examples

August 22, 2024
abstract. This project covers free semimodules and their examples. We define various algebraic structures via $\Omega$-algebras (from universal algebra) with an emphasis on semimodules. We continue to …

Monomorphisms and epimorphisms

December 17, 2022
The classes of monomorphisms, epimorphisms, bimorphisms, split monomorphisms, and split epimorphisms are closed under composition and contain all isomorsphisms. To show these classes are closed under …

hom-Sets

December 15, 2022
Let $\mathbb{C}$ be a fixed category. Consider a morphism $f:A\to B$ in $\mathbb{C}$ then, for any object $X$ in $\mathbb{C}$, …

Describing difficult spaces

December 14, 2022
The idea behind this curatorial project is to give artists a prompt describing a space that is difficult to visualise, and ask them to come up with a way of describing that space whether that be a …

M-sets and Yoneda for monoids

July 15, 2022
The Yoneda lemma says that for a category $\mathbb{C}$, an object $C$ in $\mathbb{C}$, and a functor $S:\mathbb{C}\to\textbf{Sets}$, $\operatorname{Nat}(\operatorname{hom}(C,-),S)$ is in bijection …

Free algebras by means of a universal property

June 27, 2022
Consider a vector space $V$, when $X$ is a basis of $V$, we say that $V$ is a free vector space on $X$ 1. For any vector space $V$ and $W$ and a basis $X$ of $V$, if there is a map $f:X\to W$ then …

Category of modules and category of vector spaces as algebraic categories

June 26, 2022
An algebraic category is defined to be any full subcategory of $\textbf{Alg}(\Omega)$, the catgeory of all $\Omega$-algebras. We can define various algebraic structures as algebraic categories. For …

Groupoids and skeletons of monoids and preorders

June 14, 2022
A monoid $(M,e,m)$, where $M$ is a set, $e$ an element of $M$, and $m$ an associative binary operation on $M$, can be viewed as a single object category. Take $M_0 = \{M\}$ or $M_0 = \emptyset$ and …

Exercises in category theory

June 14, 2022
(Last updated: December 2022) I will be making a series of posts that contains edited versions of some of the short answers I submitted for my category theory course at the University of Cape Town. …

Is the double twisted Möbius strip isotopic to the ordinary strip in real 3-space?

February 28, 2021
Over the past couple days I have been watching Tadashi Tokieda’s Topology and Geometry lectures, given at AIMS. I thought they would help me prepare for my first point-set topology course. The …