Vector valued Riesz distributions on Euclidian Jordan algebras

Let V be a Euclidean Jordan algebra, Гthe associated symmetric cone and G be the identity component of the linear automorphism group of Г.In this paper we associate to a certain class of spherical representations (ρ, ɛ) of G certain ɛ-valued Riesz distributions generalizing the classical scalar valued Riesz distributions on V. Our construction is motivated by the analytic theory of unitary highest weight representations where it permits to study certain holomorphic families of operator valued Riesz distributions whose positive definiteness corresponds to the unitarity of a representation of the automorphism group of the associated tube domain Г +iV.     

Pointed representations of Virasoro algebra

In this paper we study the pointed representations of the Virasoro algebra. We show that unitary irreducible pointed representations of the Virasoro algebra are Harish-Chandra representations, thus they either are of highest or lowest weights or have all weight spaces of dimension 1. Further, we prove that unitary irreducible weight representations of Virasoro superalgebras are either of highest weights or of lowest weights, hence they are also Harish-Chandra representations. This work was supported by CNSF     

On derivations of the heisenberg algebra

Derivations of the Heisenberg algebraH and some related questions are studied. The ideas and the language of formal differential geometry are used. It is proved that all derivations of this algebra are inner. The main subalgebras of the Lie algebraD(H) of all derivations ofH are distinguished, and their properties are studied. It is shown that the algebraH interpreted as a Lie algebra (with the commutator as the Lie bracket) forms a one-dimensional central extension ofD(H). Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 118. No. 2 pp. 163–189, February, 1999.     

The Schrödinger-Virasoro Lie Group and Algebra: Representation Theory and Cohomological Study

This article is devoted to an extensive study of an infinite-dimensional Lie algebra , introduced in [14] in the context of non-equilibrium statistical physics, containing as subalgebras both the Lie algebra of invariance of the free Schr?dinger equation and the central charge-free Virasoro algebra Vect(S¹). We call the Schr?dinger-Virasoro Lie algebra. We study its representation theory: realizations as Lie symmetries of field equations, coadjoint representation, coinduced representations in connection with Cartan’s prolongation method (yielding analogues of the tensor density modules for Vect(S¹)). We also present a detailed cohomological study, providing in particular a classification of deformations and central extensions; there appears a non-local cocycle. Communicated by Petr Kulish Daniel Arnaudon, in memoriam Submitted: January 17, 2006; Accepted: March 21, 2006     

Hilbert Module Realization of the Square of White Noise and Finite Difference Algebras

We develop an approach to the representations theory of the algebra of the square of white noise based on the construction of Hilbert modules. We find the unique Fock representation and show that the representation space is the usual symmetric Fock space. Although we started with one degree of freedom we end up with countably many degrees of freedom. Surprisingly, our representation turns out to have a close relation to Feinsilver's finite difference algebra. In fact, there exists a holomorphic image of the finite difference algebra in the algebra of square of white noise. Our representation restricted to this image is the Boukas representation on the finite difference Fock space. Thus we extend the Boukas representation to a bigger algebra, which is generated by creators, annihilators, and number operators.     

Classification of simple weight Virasoro modules with a finite-dimensional weight space

We show that the support of a simple weight module over the Virasoro algebra, which has an infinite-dimensional weight space, coincides with the weight lattice and that all non-trivial weight spaces of such module are infinite-dimensional. As a corollary we obtain that every simple weight module over the Virasoro algebra, having a non-trivial finite-dimensional weight space, is a Harish-Chandra module (and hence is either a simple highest or lowest weight module or a simple module from the intermediate series). This implies positive answers to two conjectures about simple pointed and simple mixed modules over the Virasoro algebra.     

CertainC*-algebras with real rank zero and their corona and multiplier algebras: II

We first determine the homotopy classes of nontrivial projections in a purely infinite simpleC*-algebraA, in the associated multiplier algebraM(A) and the corona algebraM A/A in terms ofK _*(A). Then we describe the generalized Fredholm indices as the group of homotopy classes of non-trivial projections ofA; consequently, we determine theK _*-groups of all hereditaryC*-subalgebras of certain corona algebras. Secondly, we consider a group structure of *-isomorphism classes of hereditaryC*-subalgebras of purely infinite simpleC*-algebras. In addition, we prove that ifA is aC*-algebra of real rank zero, then each unitary ofA, in caseA it unital, each unitary ofM(A) and ofM(A)/A, in caseA is nonunital but -unital, can be factored into a product of a unitary homotopic to the identity and a unitary matrix whose entries are all partial isometries (with respect to a decomposition of the identity).Partially supported by a grant from the National Science Foundation.     

Representation theory and convexity

IfS=G Exp (iW) is a complex open Ol'shanskiî semigroup, whereW is an open elliptic cone, then we considerG-biinvariant domainsD=G Exp (iD _g)S. First we show that the representation ofG×G on eachG-biinvariant irreducible reproducing kernel Hilbert space in Hol(D) is a highest weight representation whose kernel is the character of a highest weight representation ofG. In the second part of the paper we explain how to construct biinvariant Kähler structures on biinvariant Stein domains and show by a certain Legendre transform that the so obtained symplectic manifolds are isomorphic to domains in the cotangent bundleT ^* (G).     

The Six-Vertex Model at Roots of Unity and some Highest Weight Representations of the sl 2 Loop Algebra

We discuss irreducible highest weight representations of the sl₂ loop algebra and reducible indecomposable ones in association with the sl₂ loop algebra symmetry of the six-vertex model at roots of unity. We formulate an elementary proof that every highest weight representation with distinct evaluation parameters is irreducible. We present a general criteria for a highest weight representation to be irreducible. We also give an example of a reducible indecomposable highest weight representation and discuss its dimensionality. Communicated by Vincent Rivasseau Dedicated to Daniel Arnaudon Submitted: March 3, 2006; Accepted: March 13, 2006     

On the structure of an α-stratified generalized Verma module over Lie algebrasl(n, ℂ))

We study α-stratified modules of Verma type for the Lie algebrasl(n, ℂ). Necessary and sufficient conditions are established for existence of a submodule in a generalized Verma module.     

On the Reducibility of Scalar Generalized Verma Modules of Abelian Type

A parabolic subalgebra \(\mathfrak {p}\) of a complex semisimple Lie algebra \(\mathfrak {g}\) is called a parabolic subalgebra of abelian type if its nilpotent radical is abelian. In this paper, we provide a complete characterization of the parameters for scalar generalized Verma modules attached to parabolic subalgebras of abelian type such that the modules are reducible. The proofs use Jantzen’s simplicity criterion, as well as the Enright-Howe-Wallach classification of unitary highest weight modules.     

TheL ∞-representation algebra of a foundation topological semigroup

In the present paper, for a large family of topological semigroups which includes the topological groups and discrete semigroups as elementary examples, it is shown that the representation algebraR(S) is identical to the algebra of Fourier transforms onS.     

Sufficiency and strong commutants in quantum probability theory

A probability algebra (A, *, ω) consisting of a^*algebraA with a faithful state ω provides a framework for an unbounded noncommutative probability theory. A characterization of symmetric probability algebra is obtained in terms of an unbounded strong commutant of the left regular representation ofA. Existence of coarse-graining is established for states that are absolutely continuous or continuous in the induced topology. Sufficiency of a^*subalgebra relative to a family of states is discussed in terms of noncommutative Radon-Nikodym derivatives (a form of Halmos-Savage theorem), and is applied to couple of examples (including the canonical algebra of one degree of freedom for Heisenberg commutation relation) to obtain unbounded analogues of sufficiency results known in probability theory over a von Neumann algebra.     

Jacobi algebra and potentials generated by it

It is shown that the Jacobi algebraQJ(3) generates potentials that admit exact solution in relativistic and nonrelativistic quantum mechanics. Being a spectrum-generating dynamic symmetry algebra and possessing the ladder property,QJ(3) makes it possible to find the wave functions in the coordinate representation. The exactly solvable potentials specified in explicit form are regarded as a special case of a larger class of exactly solvable potentials specified implicitly. The connection between classical and quantum problems possessing exact solutions is obtained by means ofQJ(3).Donetsk State University. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 93, No. 1, pp. 3–16, October, 1992.     

Composition-diamond lemma for modules

We investigate the relationship between the Gröbner-Shirshov bases in free associative algebras, free left modules and “double-free” left modules (that is, free modules over a free algebra). We first give Chibrikov’s Composition-Diamond lemma for modules and then we show that Kang-Lee’s Composition-Diamond lemma follows from it. We give the Gröbner-Shirshov bases for the following modules: the highest weight module over a Lie algebra sl ₂, the Verma module over a Kac-Moody algebra, the Verma module over the Lie algebra of coefficients of a free conformal algebra, and a universal enveloping module for a Sabinin algebra. As applications, we also obtain linear bases for the above modules.     

The representations ofU q(SO4) andU q(SO3,1)

Summary We have considered here the (unitary) irreducible representations of theq-deformed algebraU _q(SO₄) and of theq-deformed Lorentz algebraU _q(SO_3,1). Both of them contain, as subalgebra, the algebraU _q(SO₃) which is shown to be isomorphic to the Fairlie-Odesskii algebra. As the list of pairwise nonequivalent irreps of theU _q(SO_3,1) demonstrates, the set of the parameters, which characterize such irreps is somewhat reduced (due to periodicity properties of the function w(z)=[z]_q) in comparison with that of theq=1 (classical) case. From another side, the list of unitary irreps of theU _q(SO_3,1) contains the strange series which has no classical counterpart (disappears at q=1).Published in Teoreticheskaya i Matematicheskaya Fizika. Vol. 95, No. 2, pp. 251–257, May, 1993.     

The Hilbert series of prime PI rings

We study the Hilbert series of finitely generated prime PI algebras. We show that given such an algebraA there exists some finite dimensional subspaceV ofA which contains 1 _A and generatesA as an algebra such that the Hilbert series ofA with respect to the vector spaceV is a rational function.     

Rigorous Formulation of a 2D Conformal Model in the Fock–Krein Space: Construction of the Global Op J *-Algebra of Fields and Currents

We use the formalism of the 2D massless scalar field model in an indefinite space of the Fock–Krein type as a basis for constructing a rigorous formulation of 2D quantum conformal theories. We show that the sought construction is a several-stage procedure whose central block is the construction of a new type of representation of the Virasoro algebra. We develop the first stage of this procedure, which is to construct a special global algebra of fields and currents generated by exponential generators. We obtain a system of commutation relations for the Wick-squared currents used in the definition of the Virasoro generators. We prove the existence of Wick exponentials of the current given by operator-valued generalized functions; the sought global algebra is rigorously defined as the algebra of current and field, Wick and normal exponentials on a common dense invariant domain in a Fock–Krein space.