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Kazhdan–Lusztig Polynomial
In the mathematical field of representation theory, a Kazhdan–Lusztig polynomial P_(q) is a member of a family of integral polynomials introduced by . They are indexed by pairs of elements ''y'', ''w'' of a Coxeter group ''W'', which can in particular be the Weyl group of a Lie group. Motivation and history In the spring of 1978 Kazhdan and Lusztig were studying Springer representations of the Weyl group of an algebraic group on \ell-adic cohomology groups related to unipotent conjugacy classes. They found a new construction of these representations over the complex numbers . The representation had two natural bases, and the transition matrix between these two bases is essentially given by the Kazhdan–Lusztig polynomials. The actual Kazhdan–Lusztig construction of their polynomials is more elementary. Kazhdan and Lusztig used this to construct a canonical basis in the Hecke algebra of the Coxeter group and its representations. In their first paper Kazhdan and Lusztig ment ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Representation Theory
Representation theory is a branch of mathematics that studies abstract algebraic structures by ''representing'' their elements as linear transformations of vector spaces, and studies modules over these abstract algebraic structures. In essence, a representation makes an abstract algebraic object more concrete by describing its elements by matrices and their algebraic operations (for example, matrix addition, matrix multiplication). The theory of matrices and linear operators is well-understood, so representations of more abstract objects in terms of familiar linear algebra objects helps glean properties and sometimes simplify calculations on more abstract theories. The algebraic objects amenable to such a description include groups, associative algebras and Lie algebras. The most prominent of these (and historically the first) is the representation theory of groups, in which elements of a group are represented by invertible matrices in such a way that the group operation i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anthony Joseph (mathematician)
Anthony Joseph (born 12 November 1966 in Port of Spain, Trinidad and Tobago) is a British/Trinidadian poet, novelist, musician and academic. In 2023, he was awarded the T. S. Eliot Prize for his book ''Sonnets for Albert''. Biography Joseph was born in Port of Spain, Trinidad, where he was raised by his grandparents. He began writing as a young child and cites his main influences as calypso, surrealism, jazz, the spiritual Baptist church that his grandparents attended, and the rhythms of Caribbean speech. Joseph has lived in the United Kingdom since 1989. In September 2004 he was chosen by Renaissance One and Arts Council England as one of 50 Black and Asian writers who have made major contributions to contemporary British literature, appearing in the "A Great Day in London" photograph and performing at the event at the British Library. In April 2005, he served as the British Council's first poet-in-residence at California State University, Los Angeles. Joseph holds a P ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Category O
In the representation theory of semisimple Lie algebras, Category O (or category \mathcal) is a category whose objects are certain representations of a semisimple Lie algebra and morphisms are homomorphisms of representations. Introduction Assume that \mathfrak is a (usually complex) semisimple Lie algebra with a Cartan subalgebra \mathfrak, \Phi is a root system and \Phi^+ is a system of positive roots. Denote by \mathfrak_\alpha the root space corresponding to a root \alpha\in\Phi and \mathfrak:=\bigoplus_ \mathfrak_\alpha a nilpotent subalgebra. If M is a \mathfrak-module and \lambda\in\mathfrak^*, then M_\lambda is the weight space :M_\lambda=\. Definition of category O The objects of category \mathcal O are \mathfrak-modules M such that # M is finitely generated # M=\bigoplus_ M_\lambda # M is locally \mathfrak-finite. That is, for each v \in M, the \mathfrak-module generated by v is finite-dimensional. Morphisms of this category are the \mathfrak-homomorphisms of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Algebraic Character
An algebraic character is a formal expression attached to a module in representation theory of semisimple Lie algebras that generalizes the character of a finite-dimensional representation and is analogous to the Harish-Chandra character of the representations of semisimple Lie groups. Definition Let \mathfrak be a semisimple Lie algebra with a fixed Cartan subalgebra \mathfrak, and let the abelian group A=\mathbb \mathfrak^* consist of the (possibly infinite) formal integral linear combinations of e^, where \mu\in\mathfrak^*, the (complex) vector space of weights. Suppose that V is a locally-finite weight module. Then the algebraic character of V is an element of A defined by the formula: : ch(V)=\sum_\dim V_e^, where the sum is taken over all weight spaces of the module V. Example The algebraic character of the Verma module M_\lambda with the highest weight \lambda is given by the formula : ch(M_)=\frac, with the product taken over the set of positive roots. Properti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simple Highest Weight Module
In the mathematical field of representation theory, a weight of an algebra ''A'' over a field F is an algebra homomorphism from ''A'' to F, or equivalently, a one-dimensional representation of ''A'' over F. It is the algebra analogue of a multiplicative character of a group. The importance of the concept, however, stems from its application to representations of Lie algebras and hence also to representations of algebraic and Lie groups. In this context, a weight of a representation is a generalization of the notion of an eigenvalue, and the corresponding eigenspace is called a weight space. Motivation and general concept Given a set ''S'' of n\times n matrices over the same field, each of which is diagonalizable, and any two of which commute, it is always possible to simultaneously diagonalize all of the elements of ''S''.In fact, given a set of commuting matrices over an algebraically closed field, they are simultaneously triangularizable, without needing to assume that they a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weyl Vector
In mathematics, the Weyl character formula in representation theory describes the characters of irreducible representations of compact Lie groups in terms of their highest weights. It was proved by . There is a closely related formula for the character of an irreducible representation of a semisimple Lie algebra. In Weyl's approach to the representation theory of connected compact Lie groups, the proof of the character formula is a key step in proving that every dominant integral element actually arises as the highest weight of some irreducible representation. Important consequences of the character formula are the Weyl dimension formula and the Kostant multiplicity formula. By definition, the character \chi of a representation \pi of ''G'' is the trace of \pi(g), as a function of a group element g\in G. The irreducible representations in this case are all finite-dimensional (this is part of the Peter–Weyl theorem); so the notion of trace is the usual one from linear algebra. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semisimple Lie Algebra
In mathematics, a Lie algebra is semisimple if it is a direct sum of simple Lie algebras. (A simple Lie algebra is a non-abelian Lie algebra without any non-zero proper ideals). Throughout the article, unless otherwise stated, a Lie algebra is a finite-dimensional Lie algebra over a field of characteristic 0. For such a Lie algebra \mathfrak g, if nonzero, the following conditions are equivalent: *\mathfrak g is semisimple; *the Killing form, κ(x,y) = tr(ad(''x'')ad(''y'')), is non-degenerate; *\mathfrak g has no non-zero abelian ideals; *\mathfrak g has no non-zero solvable ideals; * the radical (maximal solvable ideal) of \mathfrak g is zero. Significance The significance of semisimplicity comes firstly from the Levi decomposition, which states that every finite dimensional Lie algebra is the semidirect product of a solvable ideal (its radical) and a semisimple algebra. In particular, there is no nonzero Lie algebra that is both solvable and semisimple. Semisimple L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semisimple Lie Group
In mathematics, a Lie algebra is semisimple if it is a direct sum of modules, direct sum of simple Lie algebras. (A simple Lie algebra is a non-abelian Lie algebra without any non-zero proper Lie algebra#Subalgebras.2C ideals and homomorphisms, ideals). Throughout the article, unless otherwise stated, a Lie algebra is a finite-dimensional Lie algebra over a field of Characteristic (algebra), characteristic 0. For such a Lie algebra \mathfrak g, if nonzero, the following conditions are equivalent: *\mathfrak g is semisimple; *the Killing form, κ(x,y) = tr(ad(''x'')ad(''y'')), is non-degenerate; *\mathfrak g has no non-zero abelian ideals; *\mathfrak g has no non-zero solvable Lie algebra, solvable ideals; * the Radical of a Lie algebra, radical (maximal solvable ideal) of \mathfrak g is zero. Significance The significance of semisimplicity comes firstly from the Levi decomposition, which states that every finite dimensional Lie algebra is the semidirect product of a solvable i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Longest Element Of A Coxeter Group
In mathematics, the longest element of a Coxeter group is the unique element of maximal length in a finite Coxeter group with respect to the chosen generating set consisting of simple reflections. It is often denoted by ''w''0. See and . Properties * A Coxeter group has a longest element if and only if it is finite; "only if" is because the size of the group is bounded by the number of words of length less than or equal to the maximum. * The longest element of a Coxeter group is the unique maximal element with respect to the Bruhat order. * The longest element is an involution (has order 2: w_0^ = w_0), by uniqueness of maximal length (the inverse of an element has the same length as the element). * For any w \in W, the length satisfies \ell(w_0w) = \ell(w_0) - \ell(w). * A reduced expression for the longest element is not in general unique. * In a reduced expression for the longest element, every simple reflection must occur at least once. * If the Coxeter group is finite the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Constant Term
In mathematics, a constant term is a term in an algebraic expression that does not contain any variables and therefore is constant. For example, in the quadratic polynomial :x^2 + 2x + 3,\ the 3 is a constant term. After like terms are combined, an algebraic expression will have at most one constant term. Thus, it is common to speak of the quadratic polynomial :ax^2+bx+c,\ where x is the variable, as having a constant term of c. If the constant term is 0, then it will conventionally be omitted when the quadratic is written out. Any polynomial written in standard form has a unique constant term, which can be considered a coefficient of x^0. In particular, the constant term will always be the lowest degree term of the polynomial. This also applies to multivariate polynomials. For example, the polynomial :x^2+2xy+y^2-2x+2y-4\ has a constant term of −4, which can be considered to be the coefficient of x^0y^0, where the variables are eliminated by being exponentiated to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bruhat Order
In mathematics, the Bruhat order (also called strong order or strong Bruhat order or Chevalley order or Bruhat–Chevalley order or Chevalley–Bruhat order) is a partial order on the elements of a Coxeter group, that corresponds to the inclusion order on Schubert varieties. History The Bruhat order on the Schubert varieties of a flag manifold or a Grassmannian was first studied by , and the analogue for more general semisimple algebraic groups was studied by . started the combinatorial study of the Bruhat order on the Weyl group, and introduced the name "Bruhat order" because of the relation to the Bruhat decomposition introduced by François Bruhat. The left and right weak Bruhat orderings were studied by . Definition If (''W'', ''S'') is a Coxeter system with generators ''S'', then the Bruhat order is a partial order on the group ''W''. Recall that a reduced word for an element ''w'' of ''W'' is a minimal length expression of ''w'' as a product of elements of ''S'', and the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
