About Desvl

A blog mainly on graduate mathematics.

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The Structure of SL_2(F_3) as a Semidirect Product

1970-01-01 08:00:00

In this post we determine $SL_2(\mathbb{F}_3)$ using Sylow theory and linear algebra.

A Separable Extension Is Solvable by Radicals Iff It Is Solvable

1970-01-01 08:00:00

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.

Picard's Little Theorem and Twice-Punctured Plane

1970-01-01 08:00:00

We show that the range of a non-constant entire function's range cannot be a twice-punctured plane.

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

1970-01-01 08:00:00

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.

Important Posts of This Blog

1970-01-01 08:00:00

This post collects the top 5 most popular posts according to Google search console.

Artin's Theorem of Induced Characters

1970-01-01 08:00:00

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.

Chinese Remainder Theorem in Several Scenarios of Ring Theory

1970-01-01 08:00:00

We study the Chinese remainder theorem in various contexts and abstract levels.

Projective Representations of SO(3)

1970-01-01 08:00:00

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.

The Quadratic Reciprocity Law

1970-01-01 08:00:00

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

Vague Convergence in Measure-theoretic Probability Theory - Equivalent Conditions

1970-01-01 08:00:00

We give an introduction to vague convergence and see several equivalent conditions of it.

The Pontryagin Dual group of Q_p

1970-01-01 08:00:00

In this post we show that the Pontryagin dual group of $\mathbb{Q}_p$ is isomorphic to itself.

The Haar Measure on the Field of p-Adic Numbers

1970-01-01 08:00:00

In this post we study the canonical Haar measure on $Q_p$, and give a explicit definition just as the Lebesgue measure.

Every Regular Local Ring is Cohen-Macaulay

1970-01-01 08:00:00

In this post we show that the class of regular local rings (the abstract version of power series rings) is a subclass of Cohen-Macaulay ring.

The abc Theorem of Polynomials

1970-01-01 08:00:00

In this post we show the Mason-Stothers theorem, the so-called $abc$ theorem for polynomials, and derive Fermat's Last theorem and Davenport's inequality for polynomials. These three theorems correspond to the $abc$ conjecture, Fermat's Last Theorem and Hall's conjecture in number theory.

A Step-by-step of the Analytic Continuation of the Riemann Zeta Function

1970-01-01 08:00:00

We compute the analytic continuation of the Riemann Zeta function and after that the reader will realise that asserting $1+2+\dots=-\frac{1}{12}$ without enough caution is not a good idea.

Properties of Cyclotomic Polynomials

1970-01-01 08:00:00

In this post we study cyclotomic polynomials in field theory and deduce some baisc properties of it. We will also use it to solve some problems in field theory.

Calculus on Fields - Heights of Polynomials, Mahler's Measure and Northcott's Theorem

1970-01-01 08:00:00

We study the height of polynomials and derive some important tools.

Hensel's Lemma - A Fair Application of Newton's Method and 'Double Induction'

1970-01-01 08:00:00

We prove the celebrated Hensel's lemma using the so-called Newton's method and "double induction", and try to find solutions of polynomials in $\mathbb{Q}_p$.

Irreducible Representations of GL_2(F_q)

1970-01-01 08:00:00

In this post we follow the step of Fulton-Harris to classify all irreducible representations of $GL_2(\mathbb{F}_q)$. A character table is added at the end.

Segre Embedding And Heights

1970-01-01 08:00:00

We give a quick look at the Segre embedding and try to use that in a fundamental tool of Diophantine Geometry - heights.