Journal of Nonlinear Mathematical Physics

Volume 25, Issue 4, July 2018, Pages 518 - 527

Free-field realizations of the Wπ’œn,N-algebra

Authors
Yanyan Ge
School of Mathematical Science, University of Science and Technology of China, Hefei 230026, P.R. China,yanyange@mail.ustc.edu.cn
Kelei Tian*
School of Mathematics, Hefei university of Technology, Hefei 230009, P.R. China,kltian@ustc.edu.cn;kltian@hfut.edu.cn
Xiaoming Zhu
School of Mathematical Science, University of Science and Technology of China, Hefei 230026, P.R. China,zxm2017@mail.ustc.edu.cn
Dafeng Zuo
School of Mathematical Science, University of Science and Technology of China, Hefei 230026, P.R. China,dfzuo@ustc.edu.cn
*Corresponding author.
Corresponding Author
Kelei Tian
Received 19 September 2017, Accepted 12 April 2018, Available Online 6 January 2021.
DOI
10.1080/14029251.2018.1503397How to use a DOI?
Keywords
Wπ’œn,N , algebra; free-field realization
Abstract

In this paper, we will construct free-field realizations of the Wπ’œn,N algebra associated to an π’œn -valued differential operator

𝒧=Inβˆ‚N+UNβˆ’1βˆ‚Nβˆ’1+UNβˆ’2βˆ‚Nβˆ’2+β‹―U0,
where π’œn is a Frobenius algebra with the unit In.

Copyright
Β© 2018 The Authors. Published by Atlantis and Taylor & Francis
Open Access
This is an open access article distributed under the CC BY-NC 4.0 license (http://creativecommons.org/licenses/by-nc/4.0/).

1. Introduction

The source of the concept of W-algebras is the conformal field theory (CFT briefly) [2, 11, 23]. The main problem of the CFT is a description of fields having conformal symmetries. Only in the two-dimensional case is the group of conformal diffeomorphisms rich enough to build a meaningful theory on this base. All diffeomorphisms of a circle represent the core of the theory. Its related Lie algebra is a centerless Virasoro algebra, whose extension is the well-known Virasoro algebra. In the study of Virasoro algebra, there were various representations in terms of free fields, based on bosons, fermions and ghosts. In particular, the free-boson representation, including vertex operators, proved to be useful for particular calculations, especially for the evaluation of correlation functions.

The CFT requires the extension of the Virasoro algebra as far as possible. The work by Zamolodchikov pioneered the concept of CFT. He gave an extension of the Virasoro algebra called the W3 algebra. In that terminology, the Virasoro algebra was W2. At the end of the 1980’s, it was found that the mathematical framework for further extension of Virasoro algebra already existed as the theory of integrable systems. In other words, the classical realization of the W-algebra [23] appears naturally as the second Poisson bracket of KdV-type hierarchies. For example, the Virasoro algebra W2 is realized as the Magri bracket for the KdV hierarchy [12, 18], and the Zamolodchikov-Fateev-Lukyanov Wm-algebra as the second Adler-Gelfand-Dickey (AGD briefly) bracket for the mth-order Gelfand-Dickey (GDm) hierarchy [1, 10, 17, 19]. Free-field relations of W-algebras have also been obtained by constructing the related Miura maps, please see e.g. [7–9, 14] and references therein for details.

In [5], A. Bilal proposed a non-local matrix generalization of the well-known Wm-algebra, called the Vn,m-algebra. by constructing the second AGD bracket associated with a matrix differential operator of order m

𝔏=βˆ’Inβˆ‚m+U1βˆ‚mβˆ’1+U2βˆ‚mβˆ’2+β‹―+Um   =βˆ’(Inβˆ‚βˆ’P1)β‹―(Inβˆ‚βˆ’Pm),β€‰β€‰β€‰β€‰β€‰βˆ‚=βˆ‚βˆ‚x, Pj, Uj∈gl(n,𝔺),
where In is the nth-order identity matrix. Upon reducing to U1 = 0, the non-commutativity of matrices implies the presence of non-local terms in the Vn,m-algebra. A Miura transformation relates these Poisson brackets of the Uj to much simpler ones of a set of Pi∈gl(n,𝔺) , i.e., the Kupershmidt-Wilson (KW briefly) type theorem. Contrary to the scalar case, generally Pi are not free fields. It is difficult to give such a free-field realization because of the non-local terms except some special cases [3,4].

Recently motivated by the work in [6, 13, 16, 25], Strachan and Zuo began to study the Frobenius algebra-valued integrable systems [21, 22, 24, 26]. In [21] they introduced an 𝔉 -valued KP hierarchy associated with an 𝔉 -valued pseudo-differential operator (Ξ¨DO in brief)

L=1π”‰βˆ‚+U1βˆ‚βˆ’1+U2βˆ‚βˆ’2+β‹―
and constructed infinite series of bi-Hamiltonian structures, where 1𝔉 is the unit of the Frobenius algebra 𝔉 . Via the properties of the second Hamiltonian structures, they have obtained a local matrix generalization of W-type algebras. Because the Frobenius algebra is commutative, upon reducing to the U1 = 0, the second Hamiltonian structure is still local, which gives a chance to construct free-field realizations.

The aim of this paper is to construct free-field realizations of the Wπ’œn,N algebra associated to a concrete π’œn -valued differential operator

𝒧=Inβˆ‚N+UNβˆ’1βˆ‚Nβˆ’1+UNβˆ’2βˆ‚Nβˆ’2+β‹―U0
and organized as follows. Firstly, we recall the definition of W𝔉n,N -algebra and then show a KW-type theorem. Afterwards, with the help of the KW-type theorem we will construct the free-field realizations of the Wπ’œn,N algebra. Finally we give two examples to illustrate our method.

2. The W𝔉n,N -algebra and the KW-type theorem

2.1. Local matrix generalizations of the classical W algebras

To be self-contained, below we recall some known facts, see [21, 22] for details. Let us begin with some basic definitions.

Definition 2.1.

The Frobenius algebra 𝔉:={𝔉,tr𝔉,1𝔉,∘} over 𝕂 is a free 𝕂 -module 𝔉 of finite rank n, equipped with a commutative and associative multiplication ∘ and the unit 1𝔉 , and a 𝕂 -linear form tr𝔉:𝔉→𝕂 whose kernel contains no nontrivial ideas, where 𝕂 is 𝔺 or 𝕉 .

Let

𝒧=1π”‰βˆ‚N+UNβˆ’1βˆ‚Nβˆ’1+UNβˆ’2βˆ‚Nβˆ’2+β‹―U0 (2.1)
be an 𝔉 -valued differential operator of order N. The 𝔉 -valued Gefland-Dickey (GD in brief) hierarchy is defined as
βˆ‚π’§βˆ‚tr=Brβˆ˜π’§βˆ’π’§βˆ˜Br,   r=1,2,…, (2.2)
where Br=𝒧 +rN is the pure differential part of the operator 𝒧rN . As discussed in [21], the 𝔉 -valued GD hierarchy has bi-hamiltonian structures with the second Poisson bracket as
{f˜,g˜}(N)=trπ”‰βˆ«res((π’§βˆ˜Ξ΄fδ𝒧)+βˆ˜π’§βˆ’π’§βˆ˜(Ξ΄fΞ΄π’§βˆ˜π’§)+)°δgδ𝒧dx, (2.3)
where the variational derivative a Ξ΄fδ𝒧 is defined by the formula Ξ΄fδ𝒧=βˆ‘i=0Nβˆ’1βˆ‚βˆ’iβˆ’1Ξ΄fΞ΄Ui . Upon reducing to the UNβˆ’1=0, the Poisson bracket { , }(N) is reducible if and only if
res[𝒧,Ξ΄fδ𝒧]=0. (2.4)

We denote the reduced bracket by { , } D(N) , which provides a local matrix generalization of the classical WN-algebra ([21]). We would like to call the W𝔉n,N -algebra. Especially when one takes Ο†(x)=tr𝔉UNβˆ’2 , with the use of (2.3) and (2.4) the reduced Poisson bracket is given by

{Ο†(x),Ο†(y)} D(N)=βˆ’(N3βˆ’N12βˆ‚3+Ο†βˆ‚+βˆ‚Ο†)Ξ΄(xβˆ’y).

This means that the W𝔉n,N -algebra contains the Virasoro algebra as its subalgebra.

2.2. Modifying the second Hamiltonian structure

In order to construct free-field realizations of the W𝔉n,N -algebra, we want to study the transformation of the second Hamiltonian structure { , } by the factorization

𝒧=𝒧rβˆ˜π’§rβˆ’1βˆ˜β‹―βˆ˜π’§1, (2.5)
where 𝒧j=1π”‰βˆ‚Nj+Vj,Njβˆ’1βˆ‚Njβˆ’1+β‹― are 𝔉 -valued Ξ¨DOs and βˆ‘j=1rNr=N .

Theorem 2.1.

Assume that the factorization (2.5) exists, then the second Poisson bracket for L is a direct sum of those for 𝒧1,…,𝒧r , that is to say,

{f˜,g˜}(N)=βˆ‘j=1r{f˜,g˜}(Nj). (2.6)

Moreover, the constraint condition UNβˆ’1 = 0 is equivalent to

 res [𝒧,Ξ΄fδ𝒧]=βˆ‘j=1rres[𝒧j,Ξ΄fδ𝒧j]=0. (2.7)

When 𝔉=𝕉 , this result is the so-called KW theorem in [15].

Proof. Observe that

Ξ΄f˜=trπ”‰βˆ«resΞ΄fΞ΄π’§βˆ˜Ξ΄π’§dx=βˆ‘j=1rtrπ”‰βˆ«resΞ΄fδ𝒧j°δ𝒧jdx    =βˆ‘j=1rtrπ”‰βˆ«resΞ΄fΞ΄π’§βˆ˜π’§rβˆ˜β‹―βˆ˜π’§j+1βˆ˜Ξ΄π’§jβˆ˜π’§jβˆ’1βˆ˜β‹―βˆ˜π’§1dx    =βˆ‘j=1rtrπ”‰βˆ«res𝒧jβˆ’1βˆ˜β‹―βˆ˜π’§1∘δfΞ΄π’§βˆ˜π’§rβˆ˜β‹―βˆ˜π’§j+1βˆ˜Ξ΄π’§jdx.

This expression implies

Ξ΄fδ𝒧j=𝒧jβˆ’1βˆ˜β‹―βˆ˜π’§1∘δfΞ΄π’§βˆ˜π’§rβˆ˜β‹―βˆ˜π’§j+1  mod  R(βˆ’βˆž,βˆ’mjβˆ’1). (2.8)

Here R(βˆ’βˆž, βˆ’k) contains all of the 𝔉 -valued operators of the form βˆ‘j=βˆ’βˆžβˆ’kAjβˆ‚j . With the use of (2.8), we get

𝒧j∘δfδ𝒧j=Ξ΄fδ𝒧j+1βˆ˜π’§j+1=𝒧jβˆ˜β‹―βˆ˜π’§1∘δfΞ΄π’§βˆ˜π’§rβˆ˜β‹―βˆ˜π’§j+1  mod  R(βˆ’βˆž,βˆ’1) (2.9)
and
βˆ‘j=1rres[𝒧j,Ξ΄fδ𝒧j]=res(𝒧r∘δfδ𝒧rβˆ’Ξ΄fδ𝒧1βˆ˜π’§1)=res[𝒧,Ξ΄fδ𝒧]. (2.10)

Obviously, (2.7) follows from (2.4) and (2.10). With the help of (2.9), the right side of (2.6) is

βˆ‘j=1r{f˜,g˜}(Nj)=βˆ‘j=1rtrπ”‰βˆ«res((𝒧j∘δfδ𝒧j)+βˆ˜π’§jβˆ’π’§j∘(Ξ΄fδ𝒧jβˆ˜π’§j)+)∘δgδ𝒧jdx=βˆ‘j=1rtrπ”‰βˆ«res(𝒧j∘(Ξ΄fδ𝒧jβˆ˜π’§j)βˆ’(𝒧j∘δfδ𝒧j)βˆ’βˆ˜π’§j)∘δgδ𝒧jdx=βˆ‘j=1rtrπ”‰βˆ«res(Ξ΄fδ𝒧jβˆ˜π’§j)βˆ’βˆ˜(Ξ΄gδ𝒧jβˆ˜π’§j)+dxβˆ’βˆ‘j=1rtrπ”‰βˆ«res(𝒧j∘δfδ𝒧j)βˆ’βˆ˜(𝒧j∘δgδ𝒧j)+dx=βˆ‘j=1rtrπ”‰βˆ«res(Ξ΄fδ𝒧jβˆ˜π’§j)βˆ’βˆ˜(Ξ΄gδ𝒧jβˆ˜π’§j)+dxβˆ’βˆ‘j=1rβˆ’1trπ”‰βˆ«res(Ξ΄fδ𝒧j+1βˆ˜π’§j+1)βˆ’βˆ˜(Ξ΄gδ𝒧j+1βˆ˜π’§j+1)+dxβˆ’trπ”‰βˆ«res(𝒧r∘δfδ𝒧r)βˆ’βˆ˜(𝒧r∘δgδ𝒧r)+dx=trπ”‰βˆ«res[(Ξ΄fδ𝒧1βˆ˜π’§1)βˆ’βˆ˜(Ξ΄gδ𝒧1βˆ˜π’§1)+βˆ’(𝒧r∘δfδ𝒧r)βˆ’βˆ˜(𝒧r∘δgδ𝒧r)+]dx={f˜,g˜}(N).

We thus complete the proof of this theorem.

The above theorem implies that it is possible to simplify the construction of the free-field realization for the W𝔉n,N -algebra to the construction of the free-field realization for each copy of the W𝔉n,1 -algebra. Many examples suggest the existence of free-filed realizations of the above W-type algebras, but up to now we have no a unified proof for the general W𝔉n,N -algebra. In the next section we illustrate our construction by taking a concrete algebra π’œn .

3. Free-field realizations of the Wπ’œn,N -algebra

Let us denote

𝒡n={a=βˆ‘k=1nakΞ›kβˆ’1∣akβˆˆπ”Ί,k=1,…,n},
where Ξ›=(Ξ›ij)∈gl(n,𝔺) with the elements
Ξ›ij=Ξ΄i,j+1={1,  i=j+10,  otherΒ casesΒ 
and Ξ›0 = In is the nth-order identity matrix. Observe that Ξ›n = 0, then 𝒡n is a maximal commutative subalgebra of gl(n,𝔺) . In [21, 26] , they have shown that the algebra 𝒡n has at least n-β€œbasic” different ways to be realized as the Frobenius algebra π’œk:={𝒡n,In,trπ’œk} with the trace form defined by
trπ’œk(a)=ak+an(1βˆ’Ξ΄n,k)  for any  a=βˆ‘k=1nakΞ›kβˆ’1βˆˆπ’΅n. (3.1)

Without loss of generality, in this section we will take the Frobenius algebra 𝔉 as π’œn and construct free-field realization of Wπ’œn,N -algebra.

Suppose that the π’œn -valued differential operator

𝒧=Inβˆ‚N+UNβˆ’1βˆ‚Nβˆ’1+UNβˆ’2βˆ‚Nβˆ’2+β‹―U0
could be represented as a product of
𝒧=𝒧Nβˆ˜π’§Nβˆ’1βˆ˜β‹―βˆ˜π’§1
of π’œn -valued differential operators 𝒧i=Inβˆ‚+Vj, j=1,…,N. With the use of Theorem 2.1 , we get
{f˜,g˜}(N)=βˆ‘j=1N{f˜,g˜} 𝒧j(1)=βˆ‘j=1Ntrπ”‰βˆ«res((𝒧j∘δfδ𝒧j)+βˆ˜π’§jβˆ’π’§j∘(Ξ΄fδ𝒧jβˆ˜π’§j)+)∘δgδ𝒧jdx=βˆ‘j=1Ntrπ”‰βˆ«Ξ΄fΞ΄Vjβˆ˜βˆ‚βˆ‚xΞ΄gΞ΄Vjdx.    Here using  δfδ𝒧j=βˆ‚βˆ’1Ξ΄fΞ΄Vj. (3.2)

More precisely,

{trπ’œn∫FVidx,trπ’œn∫GVjdx}(N)=Ξ΄ijtrπ’œn∫Fβˆ‚βˆ‚xGdx,
where F and G are two π’œn -valued test functions.

Next, we want to study the reduced bracket under reduction to the submanifold UNβˆ’1 = 0.

Lemma 3.1.

The Poisson bracket { , }(N) with the constraint UNβˆ’1 = 0 is reduced to

{trπ’œn∫FVidx,trπ’œn∫GVjdx} D(N)=(Ξ΄ijβˆ’1N)trπ’œn∫Fβˆ‚βˆ‚xGdx, (3.3)
where F and G are two π’œn -valued test functions. In particular,
{Vi,q(x),Vj,r(y)} D(N)=(Ξ΄ijβˆ’1N)Ξ΄q+r,n+1Ξ΄β€²(xβˆ’y), (3.4)

where Vi=βˆ‘q=1nVi,qΞ›qβˆ’1 .

Proof. Taking an overcomplete set of vectorsb

hβ†’j=(h j1,…,h jNβˆ’1),   j=1,…,N (3.5)
in an (Nβˆ’1)-dimensional Euclidean space with
βˆ‘j=1Nhβ†’j=0,β€‰β€‰βˆ‘j=1Nh jah jb=Ξ΄ab,β€‰β€‰βˆ‘a=1Nβˆ’1h iah ja=Ξ΄ijβˆ’1N. (3.6)

Observe that UNβˆ’1=βˆ‘j=1NVj and denoting 𝒱a=βˆ‘j=1Nh jaVj , a = 1,…, N βˆ’ 1. With the help of (3.6), we have

Vj=1NUNβˆ’1+βˆ‘a=1Nβˆ’1h ja𝒱a,  j=1,…,N
and
Ξ΄fΞ΄Vj=Ξ΄fΞ΄UNβˆ’1+βˆ‘a=1Nβˆ’1h jaΞ΄fδ𝒱a,  j=1,…,N. (3.7)

So using (3.6) and (3.7), the Poisson bracket { , }(N) in (3.2) can be rewritten as

{f,g˜}(N)=βˆ‘j=1Ntrπ”‰βˆ«Ξ΄fΞ΄Vjβˆ˜βˆ‚βˆ‚xΞ΄gΞ΄Vjdx=Ntrπ”‰βˆ«Ξ΄fΞ΄UNβˆ’1βˆ˜βˆ‚βˆ‚xΞ΄gΞ΄UNβˆ’1dx+βˆ‘a=1Nβˆ’1trπ”‰βˆ«Ξ΄fδ𝒱aβˆ˜βˆ‚βˆ‚xΞ΄gδ𝒱adx.

When we consider the reduction UNβˆ’1 = 0, from (2.7) we should take into account the following condition

βˆ‘j=1N(Ξ΄fΞ΄Vj)x=0. (3.8)

That is to say.

0=βˆ‘j=1N(Ξ΄fΞ΄Vj)x=NΞ΄fΞ΄UNβˆ’1+βˆ‘j=1Nβˆ‘a=1Nβˆ’1h jaΞ΄fδ𝒱a=NΞ΄fΞ΄UNβˆ’1.

Thus the reduced Poisson bracket { , } D(N) is given by

{f˜,g˜} D(N)=βˆ‘a=1Nβˆ’1trπ”‰βˆ«Ξ΄fδ𝒱aβˆ˜βˆ‚βˆ‚xΞ΄gδ𝒱adx
and for two π’œn -valued test functions F and G,
{trπ’œn∫FVidx,trπ’œn∫GVjdx} D(N)=βˆ‘a=1Nβˆ’1h iah jatrπ’œn∫Fβˆ‚βˆ‚xGdx=(Ξ΄ijβˆ’1N)trπ’œn∫Fβˆ‚βˆ‚xGdx.

The identity (3.4) follows from the formula (3.3) and the definition tr𝔉 in (3.1).

Let K = (Kqr) be an n Γ— n matrix with the elements Kqr = Ξ΄q+r,n+1. Obvious the matrix K is a real symmetric matrix, thus there exists an orthogonal matrix Q such that K = Q diag(Ξ»1,…, Ξ»n) Qt, where Ξ»j are eigenvalues of K and Qt is the transpose of Q. Assume

S=(Sqr)=Qdiag(Ξ»1,…,Ξ»n)∈gl(n,𝔺), (3.9)

then K=S St.

Taking (Nβˆ’1)n free fields Ο†j,q (x) with the currents ji,q(x)=Ο†β€²i,q(x) together with the Poisson bracket

{ji,q(x),jj,r(y)} D(N)=Ξ΄ijΞ΄qrΞ΄β€²(xβˆ’y), (3.10)

where i, j=1,…, Nβˆ’1 and q, r = 1,…, n.

Theorem 3.1.

Setting

Jβ†’k=(J1,k,…,JNβˆ’1,k),  Ja,k=βˆ‘Ξ±=1nSk,Ξ±ja,Ξ±(x), (3.11)
then the identification 𝒧=𝒧Nβˆ˜π’§Nβˆ’1βˆ˜β‹―βˆ˜π’§1 with the element
𝒧j=Inβˆ‚+Vj=Inβˆ‚+βˆ‘k=1n(hβ†’jβ‹…Jβ†’k)Ξ›kβˆ’1,  j=1,…,N (3.12)
provides a free-field realization of the Wπ’œn,N -algebra, where hβ†’jβ‹…jβ†’k:=βˆ‘a=1Nβˆ’1h jaJa,k .

Proof. The constrained condition UNβˆ’1 = 0 follows from

βˆ‘j=1NVj=βˆ‘j=1Nβˆ‘k=1n(hβ†’jβ‹…Jβ†’k)Ξ›kβˆ’1=βˆ‘k=1n(βˆ‘j=1Nhβ†’jβ‹…jβ†’k)Ξ›kβˆ’1=0.

Denoting Vj=βˆ‘k=1nVj,k(x)Ξ›kβˆ’1 , then Vjk(x)=hβ†’jβ‹…Jβ†’k=βˆ‘a=1Nβˆ’1h jaJa,k . Now, with the help of (3.6), (3.9) and (3.10), we have

{Vi,q(x),Vj,r(y)} D(N)={hβ†’iβ‹…Jβ†’q,hβ†’jβ‹…Jβ†’r} D(m)=βˆ‘a,b=1Nβˆ’1{h iaJa,q(x),h jaJb,r(x)} D(m)=βˆ‘a,b=1Nβˆ’1h iah jbβˆ‘Ξ±,Ξ²=1n{Sq,Ξ±ja,Ξ±(x),Sr,Ξ²jb,Ξ²(x)} D(m)=βˆ‘a,b=1Nβˆ’1h iah jbβˆ‘Ξ±,Ξ²=1nSq,Ξ±Sr,Ξ²Ξ΄abδαβδ′(xβˆ’y)=βˆ‘a=1Nβˆ’1h iah jaΞ΄q+r,nβˆ’1Ξ΄β€²(xβˆ’y)=hβ†’iβ‹…hβ†’jΞ΄q+r,nβˆ’1Ξ΄β€²(xβˆ’y)=(Ξ΄ijβˆ’1N)Ξ΄q+r,nβˆ’1Ξ΄β€²(xβˆ’y),
which is exactly the reduced Poisson bracket (3.4). We thereby obtain the free-field realization of the Wπ’œn,N -algebra.

4. Conclusion

In summary, with the help of the KW-type theorem, we have constructed free-field realizations of the Wπ’œn,N algebra associated with the π’œn -valued differential operator

𝒧=Inβˆ‚N+UNβˆ’1βˆ‚Nβˆ’1+UNβˆ’2βˆ‚Nβˆ’2+β‹―U0.

By analogy with the above, a minor modification will give the free-field realizations of the Wπ’œk,N algebra for k=1,…, n βˆ’ 1. But for general W𝔉,N algebra, it is still open because of the uncertainty of the 𝕂 -linear form tr𝔉 .

Acknowledgments

The authors thanks the editors and referee’s suggestions for improving the presentation of this paper. K. Tian is supported by NSFC (11671371) and the Anhui Province Natural Science Foundation (No. 1608085MA04). D. Zuo is partially supported by NSFC (11671371) and and Wu Wen-Tsun Key Laboratory of Mathematics, CAS, USTC.

Footnotes

a

The variational derivative with respect to an algebra-valued field has been discussed in [20]. In the present context, let f˜=∫tr𝔉F(V)dx for V=βˆ‘q=1nvqeqβˆˆπ”‰ , the variational derivative Ξ΄FΞ΄V is defined by

f˜(v+Ξ΄v)βˆ’f˜(v)=∫trπ”Œ(Ξ΄FΞ΄V∘δV+o(Ξ΄V))dx=βˆ«βˆ‘q=1n(Ξ΄fΞ΄vqΞ΄vq+o(Ξ΄v))dx,
where f(v)=tr𝔉F(V),Ξ΄V=βˆ‘q=1nΞ΄vqeqβˆˆπ”‰,Ξ΄fΞ΄vq=βˆ‘j=0∞(βˆ’βˆ‚)jβˆ‚fβˆ‚v q(j) and Ξ΄v is a small parameter. Without confusion, we use the notation Ξ΄fΞ΄V instead of Ξ΄FΞ΄V .

b

e.g., such vectors have been explicitly written in [8].

References

[11]P. Di Francesco, P Mathieu, and D SΓ©nΓ©chal, Conformal Field Theory, Springer-Verlag, New York, 1997.
[23]AB Zamolodchikov, Infinite extra symmetries in two-dimensional conformal quantum field theory, Teoret. Mat. Fiz., Vol. 65, 1985, pp. 347-359.
Journal
Journal of Nonlinear Mathematical Physics
Volume-Issue
25 - 4
Pages
518 - 527
Publication Date
2021/01/06
ISSN (Online)
1776-0852
ISSN (Print)
1402-9251
DOI
10.1080/14029251.2018.1503397How to use a DOI?
Copyright
Β© 2018 The Authors. Published by Atlantis and Taylor & Francis
Open Access
This is an open access article distributed under the CC BY-NC 4.0 license (http://creativecommons.org/licenses/by-nc/4.0/).

Cite this article

TY  - JOUR
AU  - Yanyan Ge
AU  - Kelei Tian
AU  - Xiaoming Zhu
AU  - Dafeng Zuo
PY  - 2021
DA  - 2021/01/06
TI  - Free-field realizations of the Wπ’œn,N-algebra
JO  - Journal of Nonlinear Mathematical Physics
SP  - 518
EP  - 527
VL  - 25
IS  - 4
SN  - 1776-0852
UR  - https://doi.org/10.1080/14029251.2018.1503397
DO  - 10.1080/14029251.2018.1503397
ID  - Ge2021
ER  -