77 research outputs found

### A twisted conformal field theory description of dissipative quantum mechanics

We show how the recently proposed CFT for a bilayer Quantum Hall system at
filling nu=m/pm+2, the Twisted Model (TM), is equivalent to the system of two
massless scalar bosons with a magnetic boundary interaction as introduced in
Nucl. Phys. B443 (1995) 444, at the so called magic points. We are then able to
describe, within such a framework, the dissipative quantum mechanics of a
particle confined to a plane and subject to an external magnetic field normal
to it. Such an analogy is further developed in terms of the TM boundary states,
by describing the interaction between an impurity with a Hall system.Comment: 13 pages, no figures, Late

### 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

### 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

### A Cosmological Scaling Relation for Describing the Late Time Dynamics

A scaling relation between mass and minimal information of a given system is inferred from primordial black holes. Extending its validity, it is possible to describe different stages of the universe evolution. Particularly, the broad interest on matching the scaling law, from early to late redshift regimes, may suggest the mechanism to relate quantum and classical aspects of gravity. Under this hypothesis, the scaling relation is interpreted as a thermodynamic modification able to describe the cosmological dynamics at late times. In this scheme, dark energy emerges, as a consequence of assuming the validity of our scale relation. The corresponding equation of state reduces to a cosmological constant at early times and evolves in terms of the apparent horizon at late times

### 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

### Point-like topological defects in bilayer quantum Hall systems

Following a suggestion given in Phys. Lett. B 571 (2003) 250, we show how a
bilayer Quantum Hall system at fillings nu =m/pm+2 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 (cond-mat/0503478) which evidence the presence of a topological defect
in the bilayer system.Comment: 9 pages, 3 figure

### 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

### Symmetry-allowed phase transitions realized by the two-dimensional fully frustrated XY class

A 2D Fully Frustrated XY(FFXY) class of models is shown to contain a new
groundstate in addition to the checkerboard groundstates of the standard 2D
FFXY model. The spin configuration of this additional groundstate is obtained.
Associated with this groundstate there are additional phase transitions. An
order parameter accounting for these new transitions is proposed. The
transitions associated with the new order parameter are suggested to be similar
to a 2D liquid-gas transition which implies Z_2-Ising like transitions. This
suggests that the class of 2D FFXY models belongs within a U(1) x Z_2 x
Z_2-designation of possible transitions, which implies that there are seven
different possible single and combined transitions. MC-simulations for the
generalized fully frustrated XY (GFFXY) model on a square lattice are used to
investigate which of these possibilities can be realized in practice: five of
the seven are encountered. Four critical points are deduced from the
MC-simulations, three consistent with central charge c=3/2 and one with c=1.
The implications for the standard 2D FFXY-model are discussed in particular
with respect to the long standing controversy concerning the characteristics of
its phase transitions.Comment: 8 pages, 8 figure

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