Decomposition of Free Lie Algebras into Irreducible Components (original) (raw)

Let V be a representation of a finite group G. By using the trace formula for the free Lie algebra generated by V, we compute the growth of multiplicities Ž. Ž of irreducible components in ᑦ V as n varies. We also decompose L L V [ 3 n many n's satisfying some condition. We shall also see the growth of Ž. multiplicities of irreducible components in ᑦ V , where V is a represenn tation of any finite group. 127

Computing Multiplicities of Lie Group Representations

2012 IEEE 53rd Annual Symposium on Foundations of Computer Science, 2012

For fixed compact connected Lie groups H ⊆ G, we provide a polynomial time algorithm to compute the multiplicity of a given irreducible representation of H in the restriction of an irreducible representation of G. Our algorithm is based on a finite difference formula which makes the multiplicities amenable to Barvinok's algorithm for counting integral points in polytopes.

A new character formula for Lie algebras and Lie groups

Journal of Lie theory

The aim of this paper is to present a new character formula for finite-dimensional representations of finite-dimensional complex semisimple Lie Algebras and compact semisimple Lie Groups. Some applications of the new formula include the exact determination of the number of weights in a representation, new recursion formulas for multiplicities and, in some cases, closed formulas for the multiplicities themselves.

Lie elements in the group algebra

Given a representation V of a group G, there are two natural ways of defining a representation of the group algebra k[G] in the external power V^{\wedge m}. The set L(V) of elements of k[G] for which these two ways give the same result is a Lie algebra and a representation of G. For the case when G is a symmetric group and V = C^n, a permutation representation, these spaces L(C^n) are naturally embedded into one another. We describe L(C^n) for small n and formulate some questions and conjectures. This is a note on research in progress.

Two contributions to the representation theory of algebraic groups

2002

Sei V ein endlich-dimensionaler, komplexer Vektorraum. Eine Teilmenge X in V hat die Trennungseigenschaft, falls das Folgende gilt: Für je zwei linear unabhängige lineare Funktionen l, m auf V existiert ein Punkt x in X mit l(x) = 0 und m(x) = 0. Wir interessieren uns für den Fall V = C[x, y] n , d.h. V ist eine irreduzible Darstellung von SL 2 . Die Teilmengen, die wir untersuchen, sind Bahnabschlüsse von Elementen aus C[x, y] n . Wir beschreiben die Bahnen, die die Trennungseigenschaft erfüllen:

DECOMPOSITION OF TENSOR PRODUCTS OF MODULAR IRREDUCIBLE REPRESENTATIONS FOR SL3: THE p ≥ 5 CASE

We study the structure of the indecomposable direct summands of tensor products of two restricted rational simple modules for the algebraic group SL3(K), where K is an algebraically closed field of characteristic p ≥ 5. We also give a characteristicfree algorithm for the decomposition of such a tensor product into indecomposable direct summands. The p < 5 case was studied in the authors' earlier paper . We find that for characteristics p ≥ 5 all the indecomposable summands are rigid, in contrast to the characteristic 3 case.

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