Systematic approach to conformal systems with extended Virasoro symmetries

The Toda field theories, which exist for every simple Lie group, are shown to give realizations of extended Virasoro algebras that involve generators of spins higher than or equal to two. They are uniquely determined from the canonical lagrangian formalism. The quantization of the Toda field theories gives a systematic treatment of generalized conformal bosonic models. The well-known pattern of conformal field theories with non-extended Virasoro algebra, appears to be repeated for any simple group, leading to a “periodic table”, parallel to the mathematical classification of simple Lie groups.     

Two Kinds of Two-Boson Realizations of Generally Deformed Algebras with Three Generators

In this paper two kinds of two-boson realizations of generally deformed algebras with three generators are obtained by generalizing the Jordan-Schwlnger realizations of SU（2） and SU（1,1）. For each kind, a unitary realization and a non-unitary realizatlon, together with the properties of their acting spaces, are discussed. Similarity transformations that relate the non-unitary realizations to the unitary ones are given by solving unitarization equations.     

Deformation of a Virasoro algebra and the integrals of motion of the quantum sine-Gordon equation

A special deformation of a Virasoro algebra such that the screening operator is not deformed (the space where it operates is deformed) is studied. This deformation leads to a 3-index algebra. The residue of the generating function of the generators of this algebra is a generating function of the integrals of motion for the quantum sine-Gordon model. The algebra of generating functions is calculated. Explicit formulas are presented for the first few integrals of motion. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 5, 375–380 (10 March 1996)     

On the quantum super Virasoro algebra

The quantum super-algebra structure on the deformed super Virasoro algebra is investigated. More specifically we established the possibility of defining a nontrivial Hopf super-algebra on both one and two-parameters deformed super Virasoro algebras.     

Deformed fermion realization of sp(4) and its reductions

A specific q-deformation of the compact symplectic sp(4) algebra, one that is suitable for nuclear physics applications, is realized in terms of q-deformed fermion creation and annihilation operators of the shell-model. The generators of the algebra close on four distinct realizations of the u _q (2) subalgebra. These reductions, which correspond to different pairing interactions, yield a complete classification of the basis states. An analysis of the role of the q-deformation is based on a comparison of the results for energies of the lowest isovector-paired 0⁺ states in the deformed and non-deformed cases.     

A presentation for the Virasoro and super-Virasoro algebras

It is shown that the entire Virasoro, Ramond and Neveu-Schwarz algebras can each be constructed from a finite number of well-chosen generators satisfying a small number of conditions. The most economical sets consist of just two starting generators in all cases, subject to eight conditions for the Virasoro case, five conditions for the Ramond case, and nine conditions for the Neveu-Schwarz case.Work supported by the U.S. Department of Energy, Division of High Energy Physics, Contract W-31-109-ENG-38     

Realizations ofU q(su(1, 1)) by deformed quantum harmonic oscillator algebras and associated deformed Heisenberg algebras

Forsu(1, 1)-symmetric Hamiltonians of quantum mechanical systems (e.g. single-mode quantum harmonic oscillator, radial Schrödinger equation for Coulomb problem or isotropic quantum harmonic oscillator, etc.), the Heisenberg algebra of phase-space variables in two dimensions satisfy the bilinear commutation relation [ip,x]=1 (in normal units). Also there are different realizations ofsu(1, 1) by the generators of quantum harmonic oscillator algebra. We seek here the forms of deformed Heisenberg algebras (bilinear in deformedx and ip) associated with deformedsu(1, 1)-symmetric Hamiltonians. These forms are not unique in contrast to the undeformed case; and these forms are obtained here by considering different realizations of the deformedsu(1, 1) algebra by deformed oscillator algebras (satisfying different bilinear relations in deformed creation and annihilation operators), and then imposing different conditions (e.g. the deformed Heisenberg algebra of the form of the undeformed one, the form of realizations of the deformedsu(1, 1) algebra by deformed phase-space variables being the same as that ofsu(1, 1) algebra by undeformed phase-space variables, etc.), assuming linear relations between deformed phase-space variables and deformed creation-annihilation operators (as it is done in the undeformed case), we get different Heisenberg algebras. These facts are revealed in the case of a two-body Calogero model in its centre of mass frame (and for no other integrable systems in one-dimension having potential of the formV(x _i ? x_j).     

The realizations of the Lie algebraG 2

In this paper we apply a previously published method [1] to the construction of boson realizations for Lie algebraG ₂. These realizations are expressed by means of certain recurrent formulae in terms of five Bose pairs and generators of the subalgebrasl(2, R).     

Continuum Limit of the Volterra Model, Separation of Variables and Non-Standard Realizations of the Virasoro Poisson Bracket

The classical Volterra model, equipped with the Faddeev-Takhtajan Poisson bracket provides a lattice version of the Virasoro algebra. The Volterra model being integrable, we can express the dynamical variables in terms of the so-called separated variables. Taking the continuum limit of these formulae, we obtain the Virasoro generators written as determinants of infinite matrices, the elements of which are constructed with a set of points lying on an infinite genus Riemann surface. The coordinates of these points are separated variables for an infinite set of Poisson commuting quantities including L ₀. The scaling limit of the eigenvector can also be calculated explicitly, so that the associated Schroedinger equation is in fact exactly solvable.     

A quantum deformation of the Virasoro algebra and the Macdonald symmetric functions

A quantum deformation of the Virasoro algebra is defined. The Kac determinants at arbitrary levels are conjectured. We construct a bosonic realization of the quantum deformed Virasoro algebra. Singular vectors are expressed by the Macdonald symmetric functions. This is proved by constructing screening currents acting on the bosonic Fock space.     

The triviality of representations of the Virasoro algebra with vanishing central element and L0 positive

A simple and direct proof is presented that the vanishing of the central element in a representation of the Virasoro algebra with L₀ bounded below implies that all the Virasoro generators vanish. The case c ≠ 0, although inconclusive, is considered also.     

Current algebra and Wess-Zumino model in two dimensions

We investigate quantum field theory in two dimensions invariant with respect to conformal (Virasoro) and non-abelian current (Kac-Moody) algebras. The Wess-Zumino model is related to the special case of the representations of these algebras, the conformal generators being quadratically expressed in terms of currents. The anomalous dimensions of the Wess-Zumino fields are found exactly, and the multipoint correlation functions are shown to satisfy linear differential equations. In particular, Witten's non-abelean bosonisation rules are proven.     

On Equivalence of Two Realizations for a Nonlinear Lie Algebra

Recently,there are two independent approaches related to a class of nonlinear Lie algebras of three generators;and the realizations of these generators are achieved respectively in Schwinger-boson and position representation.However,by use of the representation transformation between these two representations,the equivalence of the two realizations is therefore proved.     

The Kac-moody and Virasoro commutation equations

The commutation equation of the Kac-Moody generators realized as functional differential operators is explicitly verified. The anomaly of the loop group generators is briefly discussed and the Virasoro commutation equation is then derived. No use is made of normal ordering in obtaining the central extensions of the above commutation equations.     

Construction of classical Virasoro algebras as SU(1,1) extensions

The generators of SU(1,1) and their Casimir invariant may be arrayed in a compact formula to construct all generators of the centreless Virasoro algebra which includes this SU(1,1) subalgebra. We illustrate properties of our construction through a simple differential operator realization of these algebras and comment on its usefulness.     

Electromagnetic field in two-dimensional locally flat space-time

It is shown that an infinite-dimensional symmetry is present in two-dimensional electromagnetic field theory. The generators of the ensuing Virasoro algebra are explicitly calculated both for periodic and antiperiodic fields.     

Angular quantization and form factors in massive integrable models

We discuss an application of the method of angular quantization to the reconstruction of form factors of local fields in massive integrable models. The general formalism is illustrated with examples of the Klein-Gordon, sinh-Gordon and Bullough-Dodd models. For the latter two models the angular quantization approach makes it possible to obtain free field representations for form factors of exponential operators. We discuss an intriguing relation between the free field representations and deformations of the Virasoro algebra. The deformation associated with the Bullough-Dodd models appears to be different from the known deformed Virasoro algebra.     

Multi-point local height probabilities in the integrable RSOS model

By using the bosonization technique, we derive an integral representation for multi-point Local Height Probabilities for the Andrews-Baxter-Forrester model in regime III. We argue that the dynamical symmetry of the model is provided by the deformed Virasoro algebra.