arXiv subjects

E. Ragoucy

Publications and source records attributed to E. Ragoucy.

141 records · Page 8Linked to original sources

arXiv1995

Strings from $N=2$ Gauged Wess-Zumino-Witten Models

We present an algebraic approach to string theory. An embedding of $sl(2|1)$ in a super Lie algebra together with a grading on the Lie algebra determines a nilpotent subalgebra of the super Lie algebra. Chirally gauging this subalgebra in the corresponding Wess-Zumino-Witten model, breaks the affine symmetry of the Wess-Zumino-Witten model to some extension of the $N=2$ superconformal algebra. The extension is completely determined by the $sl(2|1)$ embedding. The realization of the superconformal algebra is determined by the grading. For a particular choice of grading, one obtains in this way, after twisting, the BRST structure of a string theory. We classify all embeddings of $sl(2|1)$ into Lie super algebras and give a detailed account of the branching of the adjoint representation. This provides an exhaustive classification and characterization of both all extended $N=2$ superconformal algebras and all string theories which can be obtained in this way.

hep-th↗

arXiv1995

Linearization of W algebras and W superalgebras

In a recent paper, the authors have shown that the secondary reduction of W-algebras provides a natural framework for the linearization of W-algebras. In particular, it allows in a very simple way the calculation of the linear algebra $W(G,H)_{\geq0}$ associated to a wide class of W(G,H) algebras, as well as the expression of the W generators of W(G,H) in terms of the generators of $W(G,H)_{\geq0}$. In this paper, we present the extension of the above technique to W-superalgebras, i.e. W-algebras containing fermions and bosons of arbitrary (positive) spins. To be self-contained the paper recall the linearization of W-algebras. We include also examples such as the linearization of W_n algebras; W(sl(3|1),sl(3)) and W(osp(1|4),sp(4)) = WB_2 superalgebras.

hep-th↗

arXiv1995

Non-Polynomial Realizations of W-Algebras

Relaxing first-class constraint conditions in the usual Drinfeld-Sokolov Hamiltonian reduction leads, after symmetry fixing, to realizations of W algebras expressed in terms of all the J-current components. General results are given for G a non exceptional simple (finite and affine) algebra. Such calculations directly provide the commutant, in the (closure of) G enveloping algebra, of the nilpotent subalgebra $G_-$, where the subscript refers to the chosen gradation in G. In the affine case, explicit expressions are presented for the Virasoro, $W_3$, and Bershadsky algebras at the quantum level.

hep-th↗

arXiv1995

Slave-particle quantization and sum rules in the t-J model

In the framework of constrained systems, we give the classical Hamiltonian formulation of slave-particle models and their correct quantization. The electron-momentum distribution function in the t-J and Hubbard models is then studied in the framework of slave-particle approaches and within the decoupling scheme. We show that criticisms that have been addressed in this context coming from a violation of the sum rule for the physical electron are not valid. Due to the correct quantization rules for the slave-particles, the sum rule for the physical electron is indeed obeyed, both exactly and within the decoupling scheme.

cond-mat↗

arXiv1994

Finite W Algebras and Intermediate Statistics

New realizations of finite W algebras are constructed by relaxing the usual constraint conditions. Then, finite W algebras are recognized in the Heisenberg quantization recently proposed by Leinaas and Myrheim, for a system of two identical particles in d dimensions. As the anyonic parameter is directly associated to the W-algebra involved in the d=1 case, it is natural to consider that the W-algebra framework is well-adapted for a possible generalization of the anyon statistics.

hep-th↗

arXiv1994

Gauged W Algebras

We perform an Hamiltonian reduction on a classical \cw(\cg, \ch) algebra, and prove that we get another \cw(\cg, \ch$'$) algebra, with $\ch\subset\ch'$. In the case $\cg=S\ell(n)$, the existence of a suitable gauge, called Generalized Horizontal Gauge, allows to relate in this way two \cw-algebras as soon as their corresponding \ch-algebras are related by inclusion.

hep-th↗

arXiv1994

Quantum Hamiltonian Reduction in Superspace Formalism

Recently the quantum hamiltonian reduction was done in the case of general $s\ell(2)$ embeddings into Lie algebras and superalgebras. In this paper we extend the results to the quantum hamiltonian reduction of $N=1$ affine Lie superalgebras in the superspace formalism. We show that if we choose a gauge for the supersymmetry, and consider only certain equivalence classes of fields, then our quantum hamiltonian reduction reduces to quantum hamiltonian reduction of non-supersymmetric Lie superalgebras. We construct explicitly the super energy-momentum tensor, as well as all generators of spin 1 (and $\hf$); thus we construct explicitly all generators in the superconformal, quasi-superconformal and $\Z_2 \times \Z_2$ superconformal algebras.

hep-th↗

arXiv1993

General properties of classical W algebras

After some definitions, we review in the first part of this talk the construction and classification of classical $W$ (super)algebras symmetries of Toda theories. The second part deals with more recently obtained properties. At first, we show that chains of $W$ algebras can be obtained by imposing constraints on some $W$ generators: we call secondary reduction such a gauge procedure on $W$ algebras. Then we emphasize the role of the Kac-Moody part, when it exists, in a $W$ (super) algebra. Factorizing out this spin 1 subalgebra gives rise to a new $W$ structure which we interpret either as a rational finitely generated $W$ algebra, or as a polynomial non linear $W_\infty$ realization. (Plenary talk presented by P. SORBA at the $XXII^{th}$ International Conference on Differential Geometric Methods in Theoretical Physics. Ixtapa Mexico, September 1993.)

hep-th↗

arXiv1993

Currents on Grassmann algebras

We define currents on a Grassmann algebra $Gr(N)$ with $N$ generators as distributions on its exterior algebra (using the symmetric wedge product). We interpret the currents in terms of ${\Z}_2$-graded Hochschild cohomology and closed currents in terms of cyclic cocycles (they are particular multilinear forms on $Gr(N)$). An explicit construction of the vector space of closed currents of degree $p$ on $Gr(N)$ is given by using Berezin integration.

hep-th↗

arXiv1993

Rational $ W $ algebras from composite operators

Factoring out the spin $1$ subalgebra of a $ W $ algebra leads to a new $ W $ structure which can be seen either as a rational finitely generated $ W $ algebra or as a polynomial non-linear $ W_\infty$ realization.

hep-th↗

arXiv1993

Osp(1|2) and Sl(2) Reductions in Generalised Super-Toda Models and Factorization of Spin 1/2 Fields

I show that the classical Toda models built on superalgebras, and obtained from a reduction with respect to an $Sl(2)$ algebra, are "linearly supersymmetrizable" (by adding spin 1/2 fields) if and only if the $Sl(2)$ is the bosonic part of an $OSp(1|2)$ algebra. In that case, the model is equivalent to the one constructed from a reduction with respect to the $OSp(1|2)$ algebra, up to spin 1/2 fields. The corresponding $W$ algebras are related through a factorization of spin 1/2 fields (bosons and fermions). I illustrate this factorization on an example: the superconformal algebra built on $Sl(n+1|2)$.

hep-th↗

arXiv1993

Folding the W Algebras

In the same way the folding of the Dynkin diagram of A_{2n} (resp. A_{2n-1}) produces the B_n (resp. C_n) Dynkin diagram, the symmetry algebra W of a Toda model based on B_n (resp. C_n) can be seen as resulting from the folding of a W-algebra based on A_{2n} (resp. A_{2n-1}). More generally, W algebras related to the B-C-D algebra series can appear from W algebras related to the unitary ones. Such an approach is in particular well adapted to obtain fusion rules of W algebras based on non simply laced algebras from fusion rules corresponding to the A_n case. Anagously, super W algebras associated to orthosymplectic superalgebras are deduced from those relative to the unitary A(m,n) series.

hep-th↗

arXiv1993

Characteristic Dynkin diagrams and W-algebras

We present a classification of characteristic Dynkin diagrams for the $A_N$, $B_N$, $C_N$ and $D_N$ algebras. This classification is related to the classification of \cw(\cg,\ck) algebras arising from non-Abelian Toda models, and we argue that it can give new insight on the structure of $W$ algebras.

hep-th↗

arXiv1992

(SUPER) W Algebras from Non Abelian (SUPER) Toda Theories

A classification of (super) $W$ algebras arising from non Abelian Toda and super Toda theories is presented. This classification is based on the $Sl(2)$ or $OSp(1|2)$ sub(super)algebras of the simple Lie (super)algebra underlying the model. This allows to compute the conformal spin content of each $W$ (super)algebra. {\em Based on two lectures given by L. Frappat and E. Ragoucy at the\\ XIX International Colloquium on Group Theoretical Methods in Physics\\ Salamanca (Spain), June 29 - July 4, 1992}

hep-th↗

arXiv1992

W Algebras and Superalgebras from Constrained WZW Models: A Group Theoretical Classification

We present a classification of $W$ algebras and superalgebras arising in Abelian as well as non Abelian Toda theories. Each model, obtained from a constrained WZW action, is related with an $Sl(2)$ subalgebra (resp. $OSp(1|2)$ superalgebra) of a simple Lie algebra (resp. superalgebra) $\cg$. However, the determination of an $U(1)_Y$ factor, commuting with $Sl(2)$ (resp. $OSp(1|2)$), appears, when it exists, particularly useful to characterize the corresponding $W$ algebra. The (super) conformal spin contents of each $W$ (super)algebra is performed. The class of all the superconformal algebras (i.e. with conformal spins $s\leq2$) is easily obtained as a byproduct of our general results.

hep-th↗