Physics Letters B 760 (2016) 345–349
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Poisson–Lie T-duals of the bi-Yang–Baxter models
Ctirad Klim
ˇ
cík
Aix Marseille Université, CNRS, Centrale Marseille I2M, UMR 7373, 13453 Marseille, France
a r t i c l e i n f o a b s t r a c t
Article history:
Received
23 June 2016
Accepted
30 June 2016
Available
online 9 July 2016
Editor:
M. Cveti
ˇ
c
Keywords:
T-duality
Nonlinear
σ -models
We prove the conjecture of Sfetsos, Siampos and Thompson that suitable analytic continuations of
the Poisson–Lie T-duals of the bi-Yang–Baxter sigma models coincide with the recently introduced
generalized λ-models. We then generalize this result by showing that the analytic continuation of a
generic σ -model of “universal WZW-type” introduced by Tseytlin in 1993 is nothing but the Poisson–Lie
T-dual of a generic Poisson–Lie symmetric σ-model introduced by Klim
ˇ
cík and Ševera in 1995.
© 2016 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
1. Introduction
Two kinds of integrable nonlinear σ -models, the so-called
η-deformation of the principal chiral model [1,2] and the λ-defor-
mation
of the WZW model [3], have recently attracted much at-
tention
because of their relevance in string theory or in non-
commutative
geometry [4]. The integrability of those models was
proven at the level of the Lax pair in [2,3] and at the level of the
so called r/s exchange relations in [5]. Both the η-model and the
λ-model turned out to be deformable further to give rise to several
families of multi-parametric integrable σ -models
1
[6–8] living on
general semi-simple group targets (those families generalize some
of the integrable families of σ -models on low dimensional group
targets obtained previously in [10]).
In
three recent papers [11,12,8], there was suggested that
the η-deformation of the principal chiral model [1,2] and the
λ-deformation of the WZW model should be related by the
Poisson–Lie T-duality [13,14] followed by an appropriate analytic
continuation of the geometry of the λ-model target. In particular,
such suggestion was fully worked out for the simplest group tar-
get
SU(2) in [8] where it was shown that the Poisson–Lie T-dual of
the bi-Yang–Baxter model [7] coincides with the analytically con-
tinued
generalized λ-model [8]. Furthermore, Sfetsos, Siampos and
Thompson conjectured that the same result should hold for the
bi-Yang–Baxter model living on a general simple compact group
target. We have partially proved this conjecture in [16] in the fol-
lowing
sense: we did work with the general simple compact group
E-mail address: ctirad.klimcik@univ-amu.fr.
1
The strong integrability in the r/s-sense of the so-called bi-Yang–Baxter model
of [7] was further established in [9].
target but we have switched off one of the two deformation pa-
rameters
of the bi-Yang–Baxter model. Said in other words, we
have established in [16] for every simple compact group target
that the Poisson–Lie T-dual of the Yang–Baxter model [1,2] coin-
cides
with the analytically continued λ-deformation of the WZW
model [3]. The first purpose of the present letter is to switch on
also the second parameter and, hence, to prove the conjecture of
Sfetsos, Siampos and Thompson in its strongest form.
The
second purpose of our work is to reveal a highly nontriv-
ial
structural relation between two classes of σ -models introduced
more than twenty years ago: the class of “universal WZW-type
conformal σ -models” introduced by Tseytlin in [18]; we shall re-
fer
to them as T-models; and the class of “Poisson–Lie T-dualizable
σ -models on a compact group target” introduced by Klim
ˇ
cík and
Ševera in [14]; we shall call them KS-models. Namely, we show
that the T-models are nothing but the analytic continuations of
the Poisson–Lie T-duals of the KS-models.
By
the way, we find truly remarkable that the T-models and the
KS-models were orbiting around for two decades without “know-
ing
about each other”. The reason for this is that the authors of
[14] have worked out the target space geometries of the Poisson–
Lie
T-duals of the KS-models in coordinates natural from the point
of view of Poisson-geometry but not natural for the comparison
with the T-model. The parametrization of the dual target suitable
for this comparison was introduced in [16] and here we use it to
establish the announced result. We find also interesting that the
KS-models were originally invented as new objects, the reason of
existence of which was their T-dualizability of a new kind, and the
authors of [14] were not aware that those models were closely re-
lated
to the T-models already existing on the market which had
their independent reason of existence.
http://dx.doi.org/10.1016/j.physletb.2016.06.077
0370-2693/
© 2016 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by
SCOAP
3
.