1,621 research outputs found
Quantum Hall Smectics, Sliding Symmetry and the Renormalization Group
In this paper we discuss the implication of the existence of a sliding
symmetry, equivalent to the absence of a shear modulus, on the low-energy
theory of the quantum hall smectic (QHS) state. We show, through
renormalization group calculations, that such a symmetry causes the naive
continuum approximation in the direction perpendicular to the stripes to break
down through infrared divergent contributions originating from naively
irrelevant operators. In particular, we show that the correct fixed point has
the form of an array of sliding Luttinger liquids which is free from
superficially "irrelevant operators". Similar considerations apply to all
theories with sliding symmetries.Comment: 7 pages, 3 figure
Functional integral over velocities for a spinning particle with and without anomalous magnetic moment in a constant electromagnetic field
The technique of functional integration over velocities is applied to the
calculation of the propagator of a spinning particle with and without anomalous
magnetic moment. A representation for the spin factor is obtained in this
context for the particle in a constant electromagnetic field. As a by-product,
we also obtain a Schwinger representation for the first case.Comment: latex, 19 page
Vacuum properties of a Non-Local Thirring-Like Model
We use path-integral methods to analyze the vacuum properties of a recently
proposed extension of the Thirring model in which the interaction between
fermionic currents is non-local. We calculate the exact ground state wave
functional of the model for any bilocal potential, and also study its
long-distance behavior. We show that the ground state wave functional has a
general factored Jastrow form. We also find that it posess an interesting
symmetry involving the interchange of density-density and current-current
interactions.Comment: 25 pages, latex, no figure
Quantum motion in superposition of Aharonov-Bohm with some additional electromagnetic fields
The structure of additional electromagnetic fields to the Aharonov-Bohm
field, for which the Schr\"odinger, Klein-Gordon, and Dirac equations can be
solved exactly are described and the corresponding exact solutions are found.
It is demonstrated that aside from the known cases (a constant and uniform
magnetic field that is parallel to the Aharonov-Bohm solenoid, a static
spherically symmetrical electric field, and the field of a magnetic monopole),
there are broad classes of additional fields. Among these new additional fields
we have physically interesting electric fields acting during a finite time, or
localized in a restricted region of space. There are additional time-dependent
uniform and isotropic electric fields that allow exact solutions of the
Schrodinger equation. In the relativistic case there are additional electric
fields propagating along the Aharonov-Bohm solenoid with arbitrary electric
pulse shape
Evidence for the PSL(22) Wess-Zumino-Novikov-Witten model as a model for the plateau transition in Quantum Hall effect: Evaluation of numerical simulations
In this paper I revise arguments in favour of the PSL(22)
Wess-Zumino-Novikov-Witten (WZNW) model as a theory of the plateau transition
in Integer Quantum Hall effect. I show that all available numerical data
(including the correlation length exponent ) are consistent with the
predictions of such WZNW model with the level .Comment: 11 pages, no figure
Gauge Fixing and BFV Quantization
Nonsingularity conditions are established for the BFV gauge-fixing fermion
which are sufficient for it to lead to the correct path integral for a theory
with constraints canonically quantized in the BFV approach. The conditions
ensure that anticommutator of this fermion with the BRST charge regularises the
path integral by regularising the trace over non-physical states in each ghost
sector. The results are applied to the quantization of a system which has a
Gribov problem, using a non-standard form of the gauge-fixing fermion.Comment: 14 page
Spin-1 chain with spin-1/2 excitations in the bulk
We present a spin-1 chain with a Hamiltonian which has three exactly solvable
ground states. Two of these are fully dimerized, analogous to the
Majumdar-Ghosh (MG) states of a spin-1/2 chain, while the third is of the
Affleck-Kennedy-Lieb-Tasaki (AKLT) type. We use variational and numerical
methods to study the low-energy excitations which interpolate between these
ground states in different ways. In particular, there is a spin-1/2 excitation
which interpolates between the MG and AKLT ground states; this is the lowest
excitation of the system and it has a surprisingly small gap. We discuss
generalizations of our model of spin fractionalization to higher spin chains
and higher dimensions.Comment: 7 pages including 4 figures; this is the published version of the
pape
Anomalous Noise in the Pseudogap Regime of YBaCuO
An unusual noise component is found near and below about 250 K in the normal
state of underdoped YBCO and Ca-YBCO films. This noise regime, unlike the more
typical noise above 250 K, has features expected for a symmetry-breaking
collective electronic state. These include large individual fluctuators, a
magnetic sensitivity, and aging effects. A possible interpretation in terms of
fluctuating charge nematic order is presented.Comment: 4 pages, 4 figure
One-electron self energies and spectral functions for the t-J model in the large-N limit
Using a recently developed perturbative approach, which considers Hubbard
operators as fundamental excitations, we have performed electronic self-energy
and spectral function calculations for the model on the square lattice.
We have found that the spectral functions along the Fermi surface are
isotropic, even close to the critical doping where the -density wave phase
takes place. Fermi liquid behavior with scattering rate and a
finite quasiparticle weight was obtained. decreases with decreasing
doping taking low values for low doping. Results are compared with other ones,
analytical and numerical like slave-boson and Lanczos diagonalization finding
agreement. We discuss our results in the light of recent experiments in
cuprates.Comment: 10 pages, 9 figures, accepted for publication in Phys. Rev.
Topological Protection and Quantum Noiseless Subsystems
Encoding and manipulation of quantum information by means of topological
degrees of freedom provides a promising way to achieve natural fault-tolerance
that is built-in at the physical level. We show that this topological approach
to quantum information processing is a particular instance of the notion of
computation in a noiseless quantum subsystem. The latter then provide the most
general conceptual framework for stabilizing quantum information and for
preserving quantum coherence in topological and geometric systems.Comment: 4 Pages LaTeX. Published versio
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