252 research outputs found
Jain states on a torus: an unifying description
We analyze the modular properties of the effective CFT description for Jain
plateaux corresponding to the fillings nu=m/(2pm+1). We construct its
characters for the twisted and the untwisted sector and the diagonal partition
function. We show that the degrees of freedom entering the partition function
go to complete a Z_{m}-orbifold construction of the RCFT U(1)xSU(m)$ proposed
for the Jain states. The resulting extended algebra of the chiral primary
fields can be also viewed as a RCFT extension of the U(1)xW(m) minimal models.
For m=2 we prove that our model, the TM, gives the RCFT closure of the extended
minimal models U(1)xW(2).Comment: 27 pages, Latex, JHEP style, no figure
Tunnelling Effects in a Brane System and Quantum Hall Physics
We argue that a system of interacting D-branes, generalizing a recent
proposal, can be modelled as a Quantum Hall fluid. We show that tachyon
condensation in such a system is equivalent to one particle tunnelling. In a
conformal field theory effective description, that induces a transition from a
theory with central charge c=2 to a theory with c=3/2, with a corresponding
symmetry enhancement.Comment: 12 pages, no figures, Latex, some aspects clarified, sect.3 expanded,
references adde
T-Dualities and Doubled Geometry of the Principal Chiral Model
The Principal Chiral Model (PCM) defined on the group manifold of SU(2) is
here investigated with the aim of getting a further deepening of its relation
with Generalized and Doubled Geometry. A one-parameter family of equivalent
Hamiltonian descriptions is introduced, and cast into the form of Born
geometries. Then O(3,3) duality transformations of the target phase space are
performed and we show that the resulting dual models are defined on the group
SB(2,C) which is the Poisson-Lie dual of SU(2) in the Iwasawa decomposition of
the Drinfel'd double SL(2, C). Moreover, starting from the Lagrangian approach,
a new kind of duality is found between the SU(2) PCM and the natural one
defined on SB(2,C) which is not an isometry of the target phase space. A parent
action with doubled degrees of freedom and configuration space SL(2, C) is then
defined that reduces to either one of the dually related models, once suitable
constraints are implemented.Comment: 41 pages, revised version published in JHE
A conformal field theory description of the paired and parafermionic states in the quantum Hall effect
We extend the construction of the effective conformal field theory for the
Jain hierarchical fillings proposed in cond-mat/9912287 to the description of a
quantum Hall fluid at non standard fillings nu=m/(pm+2). The chiral primary
fields are found by using a procedure which induces twisted boundary conditions
on the m scalar fields; they appear as composite operators of a charged and
neutral component. The neutral modes describe parafermions and contribute to
the ground state wave function with a generalized Pfaffian term. Correlators of
Ne electrons in the presence of quasi-hole excitations are explicitly given for
m=2.Comment: 11 pages, plain Late
Transport properties in bilayer Quantum Hall systems in the presence of a topological defect
Following a suggestion given in Phys. Lett. B 571(2003) 621, we show how a
bilayer Quantum Hall system at fillings nu =1/p+1 can exhibit a point-like
topological defect in its edge state structure. Indeed our CFT theory for such
a system, the Twisted Model (TM), gives rise in a natural way to such a feature
in the twisted sector. Our results are in agreement with recent experimental
findings (Phys. Rev. B 72 (2005) 041305) which evidence the presence of a
topological defect in the transport properties of the bilayer system.Comment: 10 pages, 4 figures; talk given by A. Naddeo at "X Training Course in
the Physics of Correlated Electron Systems and High-Tc Superconductors,
Vietri sul Mare (SA),Italy, 3-14 October 200
A twisted conformal field theory description of the Quantum Hall Effect
We construct an effective conformal field theory by using a procedure which
induces twisted boundary conditions for the fundamental scalar fields. That
allows to describe a quantum Hall fluid at Jain hierarchical filling,
nu=m/(2pm+1), in terms of one charged scalar field and m-1 neutral ones. Then
the resulting algebra of the chiral primary fields is U(1)xW_m. Finally the
ground state wave functions are given as correlators of appropriate composite
fields (a-electrons).Comment: 11 pages, plain Late
Twisted CFT and bilayer Quantum Hall systems
We identify the impurity interactions of the recently proposed CFT
description of a bilayer Quantum Hall system at filling nu =m/(pm+2) in Mod.
Phys. Lett. A 15 (2000) 1679. Such a CFT is obtained by m-reduction on the one
layer system, with a resulting pairing symmetry and presence of quasi-holes.
For the m=2 case boundary terms are shown to describe an impurity interaction
which allows for a localized tunnel of the Kondo problem type. The presence of
an anomalous fixed point is evidenced at finite coupling which is unstable with
respect to unbalance and flows to a vacuum state with no quasi-holes.Comment: 15 pages, 1 figure, Late
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