The property of some finite W-algebras to appear as the commutant of a particular subalgebra in a simple Lie algebra G is exploited for the obtention of new G-realizations from a "canonical" differential one.The method is applied to the conformal algebra so(4, 2) and therefore yields also results for its Poincaré subalgebra. Unitary irreducible representations of these algebras are recognized in this approach, which is naturally compared -or associated-to the induced representation technic.
IntroductionAs shown in [1,2], the construction of finite W-algebras achieved in the framework of Hamiltonian reduction [3] also leads to the determination of the commutants, in the enveloping algebra 1 U (G), of particular subalgebras of a simple Lie algebra G.Such a property can be used to build, from a special realization of G, a large class of Grepresentations. Let us be more specific, and consider a graded decomposition of the simple Lie algebra G of the typewith the corresponding commutation relations:As reminded in section 2, it is possible to recognize in the commutant of a G-subalgebra G of the formThe determination of the realization of the W-algebra needed for our purpose can be obtained in a systematic way after some modification [2] of the usual Hamiltonian reduction technic [4]. Moreover, one knows how to construct a realization of the G with differential operators on the space of smooth functions ϕ(y 1 , . . . , y s ) with s = dimG − . In this picture, the abelianity of the G −1 -part allows each G −1 generator to act by direct multiplication:-cf action of the translation group-while the generators of the G 0 ⊕G + part will be represented by polynomials in the y i and ∂ y i (see section 3). It is from this particular -canonical-differential realization of G that new representations will be constructed with the use of the finite W-algebra above mentioned. Realization of the G generators will not be affected in this approach. On the contrary, to the differential form of each generator in the G \ G part will be added a sum of W-generators, the coefficients of which are functions f (y i , ∂ y i ). By associating a matrix differential realization to each irreducible finite dimensional W-representation, one will get an action of G on vector functions ϕ = (ϕ 1 , . . . , ϕ d ), with ϕ i = ϕ i (y 1 , . . . , y s ), where d is the dimension of the considered Wrepresentation.Such an approach has already been considered with some success [1] for the study of the Heisenberg quantization for a system of two particles in 1 and 2 dimensions [5]. The corresponding algebras are respectively sp(2) and sp(4), and in each case, it has been possible to relate the anyonic parameter to the eigenvalues of a W-generator.It has seemed to us of some interest to apply our technic on a rather well-known algebra, the so(4, 2) one, also called the 4-dimensional conformal algebra. The decomposition of interest is the one in which the G −1 part is constituted by the four translations, G 0 by the Lorentz algebra so(3, 1) plus the dilata...