Mathematics. Articles in English (et en français dans le futur).

Artin-Schreier Extensions

We are interested in a special category of field extensions. Let $K$ be a field of characteristic $p \ne 0$, we want to know the structure of an extension of $K$ of degree $p$. It turns out that there lies the an Artin-Schreier polynomial of the form $X^p-X-\alpha$.
Artin-Schreier Extensions

Equivalent Conditions of Regular Local Rings of Dimension 1

In this post we collect and prove (as detailed as possible) the equivalent conditions of being a Regular local ring of dimension 1.
Equivalent Conditions of Regular Local Rings of Dimension 1

The Structure of SL_2(F_3) as a Semidirect Product

In this post we determine $SL_2(\mathbb{F}_3)$ using Sylow theory and linear algebra.
The Structure of SL_2(F_3) as a Semidirect Product

A Separable Extension Is Solvable by Radicals Iff It Is Solvable

We show that a separable extension is solvable by radical iff it is solvable, i.e. it has a Galois closure with solvable Galois group. The proof is done in a general setting.
A Separable Extension Is Solvable by Radicals Iff It Is Solvable

Picard's Little Theorem and Twice-Punctured Plane

We show that the range of a non-constant entire function's range cannot be a twice-punctured plane.
Picard's Little Theorem and Twice-Punctured Plane

SL(2,R) As a Topological Space and Topological Group

In this post we show that $SL(2,\mathbb{R})$ can be identified as the inside of a solid torus and see what we can learn from it.
SL(2,R) As a Topological Space and Topological Group

Artin's Theorem of Induced Characters

We give a relatively more detailed proof of Artin's theorem in representation theory of finite groups as well as an example of dihedral group.
Artin's Theorem of Induced Characters

Chinese Remainder Theorem in Several Scenarios of Ring Theory

We study the Chinese remainder theorem in various contexts and abstract levels.
Chinese Remainder Theorem in Several Scenarios of Ring Theory

Projective Representations of SO(3)

In this post we study projective representations of $SO(3)$, although we will make more use of $SU(2)$. At the end of this post we reach the conclusion that one will think about polynomials with odd or even terms. Projective representations have its own significance in physics although the room of this post is too small to contain it. Nevertheless, the reader is invited to use linear algebra much more extensively with a taste of modern physics in this post.
Projective Representations of SO(3)

The Quadratic Reciprocity Law

In this post we deliver the basic computation of the quadratic reciprocity law and see its importance in algebraic number theory.
The Quadratic Reciprocity Law