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Representation Theory

Algebra

Representation theory is the branch of mathematics that studies abstract algebraic structures, chiefly groups, by representing their elements as linear transformations of vector spaces, turning abstract symmetry into the concrete language of matrices. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/

Facts
Central Question
Given an abstract group or algebra, which of its representations are irreducible, the basic building blocks every other representation decomposes into, and can the irreducible representations be listed completely. 1
Key Debate
Whether every irreducible representation of interest can be classified explicitly. The classification is essentially complete for finite and compact groups, but an effective description of the unitary dual, the full set of irreducible unitary representations, remains an open problem for the noncompact real reductive Lie groups central to mathematical physics. 1
Classification
Pure or Applied
Pure Mathematics 1
Connections

Associated With

Includes

Source Frobenius reciprocity, Wikipedia
Source Issai Schur (Wikipedia)
Source Levi decomposition, Wikipedia
Source Lie-Kolchin theorem, Wikipedia
Matrix, Concepts
Source Weyl's theorem on complete reducibility, Wikipedia
Source Wigner-Eckart theorem, Wikipedia
Source Wikipedia: Young tableau
Sources
1. Wikipedia: Representation Theory
Wikimedia Foundation
  • Lead section
    Representation theory is a branch of mathematics that studies abstract algebraic structures by representing their elements as linear transformations of vector spaces.
  • Subrepresentations, quotients and irreducible representations section
    Irreducible representations are the building blocks of representation theory for many groups: if a representation V is not irreducible then it is built from a subrepresentation and a quotient that are both simpler in some sense.
  • Unitary representations section
    An effective description of the unitary dual, even for relatively well-behaved groups such as real reductive Lie groups, remains an important open problem in representation theory.
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Stone-Weierstrass Theorem (Wikipedia)
Wikipedia
  • lead paragraph
    Representation theory is a branch of mathematics that studies abstract algebraic structures by representing their elements as linear transformations of vector spaces.
  • Unitary representations section
    An effective description of the unitary dual, even for relatively well-behaved groups such as real reductive Lie groups (discussed below), remains an important open problem in representation theory.
View the Source
Weyl's theorem on complete reducibility, Wikipedia
Includes: Weyl's Theorem on Complete Reducibility, Lead sentence
Quote, Includes: Weyl's Theorem on Complete Reducibility, Lead sentence
Lie algebra representations (specifically in the representation theory of semisimple Lie algebras).
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Wigner-Eckart theorem, Wikipedia
Includes: Wigner-Eckart Theorem, Lead sentenceView the Source
Wikipedia: Young tableau
Includes: Young Tableau, Lead sentence
Quote, Includes: Young Tableau, Lead sentence
al: tableaux) is a combinatorial object useful in representation theory and Schubert calculus.
View the Source
Frobenius reciprocity, Wikipedia
Includes: Frobenius Reciprocity Theorem, Lead sentence
Quote, Includes: Frobenius Reciprocity Theorem, Lead sentence
In mathematics, and in particular representation theory, Frobenius reciprocity is a theorem expressing a duality between the proce
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Lie-Kolchin theorem, Wikipedia
Includes: Lie-Kolchin Theorem, Lead sentenceView the Source
Levi decomposition, Wikipedia
Includes: Levi Decomposition Theorem, Lead sentenceView the Source
Issai Schur (Wikipedia)
Includes: Issai Schur, Lead paragraph [in-branch]
Quote, Includes: Issai Schur, Lead paragraph [in-branch]
group representations
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