Matrix representations | Representation theory episode 2

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#grouptheory #linearalgebra #matrices #representationtheory

Whether it's classical mechanics or quantum particles, physics makes heavy use of vectors. When a physical system satisfies a set of symmetries, we have to implement those symmetries as matrices. That way, they can operate directly on all those vectors. Welcome to the world of matrix representations.

Many thanks to professor Karel Dekimpe from the university of Leuven for helping me understand representations and characters.

Don't forget to check out these links:

Wikipedia article about the regular representation.

Wikipedia article about the permutation representations in general.

A good introduction to representation theory for beginners.

A free PDF book full of great examples. It builds up the theory from the ground up, and contains all the proofs in a logical order. Quite a challenging read.

Another free PDF about representation theory.

Tobias Osborne: How representations are used in physics. He explains the theory and all the proofs in detail. By giving many specific examples, he manages to convince you of just how important representation theory is. Highly recommended.

0:00 Introduction
0:35 The group of rotations of a square
1:13 A matrix representation must be a homomorphism
2:45 A group has many different matrix representations
5:13 The regular representation
6:26 Matrix representations are essential for physics
8:57 Creating new representations from existing ones
11:13 The homomorphism restricts the matrices
12:55 Decomposing representations into smaller pieces

This video is published under a CC Attribution license
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This makes me want to dive back into shilov chapter 1!

callmedeno
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I guess we should add category theory and make more arrows :D

DeathSugar
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Just watched the previous episode! Very glad to watch this one. Take care

carloselfrancos
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Great! I wish I had your skill explaining ideas ❤ If you want to see some realtime sims, come have a look at my latest stuff, you might be interested to see the emergent properties if these arrangements

AxisSage
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Serious shit. I'm very curious to see some representations of the dihedral groups, apart from the obvious "geometric" one as orthogonal 2x2 matrices or as permutation matrices

cosimobaldi
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...When the differential equations have a physical manifestation: Represent!
What's your vector victor.

TurboLoveTrain
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A representation of an algebra A is an A-Module 🤗

Vannishn
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