Symmetry | Representation theory | Group theory

Irreducible representation

In mathematics, specifically in the representation theory of groups and algebras, an irreducible representation or irrep of an algebraic structure is a nonzero representation that has no proper nontrivial subrepresentation , with closed under the action of . Every finite-dimensional unitary representation on a Hilbert space is the direct sum of irreducible representations. Irreducible representations are always indecomposable (i.e. cannot be decomposed further into a direct sum of representations), but converse may not hold, e.g. the two-dimensional representation of the real numbers acting by upper triangular unipotent matrices is indecomposable but reducible. (Wikipedia).

Video thumbnail

RT8.2. Finite Groups: Classification of Irreducibles

Representation Theory: Using the Schur orthogonality relations, we obtain an orthonormal basis of L^2(G) using matrix coefficients of irreducible representations. This shows the sum of squares of dimensions of irreducibles equals |G|. We also obtain an orthonormal basis of Class(G) usin

From playlist Representation Theory

Video thumbnail

Representation theory: Orthogonality relations

This lecture is about the orthogonality relations of the character table of complex representations of a finite group. We show that these representations are unitary and deduce that they are all sums of irreducible representations. We then prove Schur's lemma describing the dimension of t

From playlist Representation theory

Video thumbnail

RT8.3. Finite Groups: Projection to Irreducibles

Representation Theory: Having classified irreducibles in terms of characters, we adapt the methods of the finite abelian case to define projection operators onto irreducible types. Techniques include convolution and weighted averages of representations. At the end, we state and prove th

From playlist Representation Theory

Video thumbnail

Abstract Algebra | Irreducibles and Primes in Integral Domains

We define the notion of an irreducible element and a prime element in the context of an arbitrary integral domain. Further, we give examples of irreducible elements that are not prime. Please Subscribe: https://www.youtube.com/michaelpennmath?sub_confirmation=1 Personal Website: http://

From playlist Abstract Algebra

Video thumbnail

Representation theory: Introduction

This lecture is an introduction to representation theory of finite groups. We define linear and permutation representations, and give some examples for the icosahedral group. We then discuss the problem of writing a representation as a sum of smaller ones, which leads to the concept of irr

From playlist Representation theory

Video thumbnail

RT6. Representations on Function Spaces

Representation Theory: We note how to transfer a group action of a group G on a set X to a group action on F(X), the functions on X. Because F(X) is a vector space, we obtain a representation of the group, and we can apply previous techniques. In particular, the group acts on itself in

From playlist Representation Theory

Video thumbnail

Alina Ostafe: Dynamical irreducibility of polynomials modulo primes

Abstract: In this talk we look at polynomials having the property that all compositional iterates are irreducible, which we call dynamical irreducible. After surveying some previous results (mostly over finite fields), we will concentrate on the question of the dynamical irreducibility of

From playlist Number Theory Down Under 9

Video thumbnail

Irreducible Polynomials

In this video I discuss irreducible polynomials and tests for irreducibility. Note that this video is intended for students in abstract algebra and is not appropriate for high-school or early college level algebra courses.

From playlist Abstract Algebra

Video thumbnail

RT7.3. Finite Abelian Groups: Convolution

Representation Theory: We define convolution of two functions on L^2(G) and note general properties. Three themes: convolution as an analogue of matrix multiplication, convolution with character as an orthogonal projection on L^2(G), and using using convolution to project onto irreduci

From playlist Representation Theory

Video thumbnail

Henniart: Classification des représentations admissibles irréductibles modulo p...

Recording during the thematicmeeting : "Algebraic and Finite Groups, Geometry and Representations. Celebrating 50 Years of the Chevalley Seminar " the September 23, 2014 at the Centre International de Rencontres Mathématiques (Marseille, France) Filmmaker: Guillaume Hennenfent Find this

From playlist Partial Differential Equations

Video thumbnail

Nonlinear algebra, Lecture 9: "Representation Theory", by Mateusz Michalek

This is the ninth lecture in the IMPRS Ringvorlesung, the advanced graduate course at the Max Planck Institute for Mathematics in the Sciences.

From playlist IMPRS Ringvorlesung - Introduction to Nonlinear Algebra

Video thumbnail

RT8.1. Schur Orthogonality Relations

Representation Theory of Finite Groups: As a first step to Fourier analysis on finite groups, we state and prove the Schur Orthogonality Relations. With these relations, we may form an orthonormal basis of matrix coefficients for L^(G), the set of functions on G. We also define charac

From playlist *** The Good Stuff ***

Video thumbnail

On characterization of monomial irreducible representations by Pooja Singla

DATE & TIME 05 November 2016 to 14 November 2016 VENUE Ramanujan Lecture Hall, ICTS Bangalore Computational techniques are of great help in dealing with substantial, otherwise intractable examples, possibly leading to further structural insights and the detection of patterns in many abstra

From playlist Group Theory and Computational Methods

Video thumbnail

Representation Theory(Repn Th) 3 by Gerhard Hiss

DATE & TIME 05 November 2016 to 14 November 2016 VENUE Ramanujan Lecture Hall, ICTS Bangalore Computational techniques are of great help in dealing with substantial, otherwise intractable examples, possibly leading to further structural insights and the detection of patterns in many abstra

From playlist Group Theory and Computational Methods

Video thumbnail

Representation Theory(Repn Th) 1 by Gerhard Hiss

DATE & TIME 05 November 2016 to 14 November 2016 VENUE Ramanujan Lecture Hall, ICTS Bangalore Computational techniques are of great help in dealing with substantial, otherwise intractable examples, possibly leading to further structural insights and the detection of patterns in many abstra

From playlist Group Theory and Computational Methods

Video thumbnail

Character Tables for S4 and A4

Representation Theory of Finite Groups: We build the character tables for S4 and A4 from scratch. As an application, we use irreducible characters to decompose a tensor product.

From playlist Representation Theory

Video thumbnail

Abstract Algebra | Irreducible polynomials

We introduce the notion of an irreducible polynomial over the ring k[x] where k is any field. A proof that p(x) is irreducible if and only if (p(x)) is maximal is also given, along with some examples. Please Subscribe: https://www.youtube.com/michaelpennmath?sub_confirmation=1 Personal W

From playlist Abstract Algebra

Video thumbnail

Chemistry 107. Inorganic Chemistry. Lecture 04

UCI Chemistry: Inorganic Chemistry (Fall 2014) Lec 04. Inorganic Chemistry -- Character Tables and One Application of Symmetry View the complete course: http://ocw.uci.edu/courses/chem_107_inorganic_chemistry.html Instructor: Matthew D. Law License: Creative Commons CC-BY-SA Terms of Use:

From playlist Chem 107: Week 2

Related pages

Representation theory of the Poincaré group | Modular representation theory | Character theory | Linear subspace | Representation theory of the Galilean group | Theorem of the highest weight | Vector space | Block matrix | Group (mathematics) | Identity element | Identity matrix | Root of unity | Diagonal matrix | Representation theory of diffeomorphism groups | Algebra over a field | Indecomposable module | General linear group | Homomorphism | Representation theory | Matrix similarity | Unipotent | Representation theory of SL2(R) | Characteristic (algebra) | Mathematics | Field (mathematics) | Simple module | Real number | Representation theory of SU(2) | Direct sum | Regular representation | Hilbert space | Complex number | Group homomorphism | Matrix multiplication | Matrix (mathematics) | Unitary representation