1,017 research outputs found
Optical Hall Effect in the Integer Quantum Hall Regime
Optical Hall conductivity is measured from the Faraday
rotation for a GaAs/AlGaAs heterojunction quantum Hall system in the terahertz
frequency regime. The Faraday rotation angle ( fine structure constant
mrad) is found to significantly deviate from the Drude-like behavior to
exhibit a plateau-like structure around the Landau-level filling . The
result, which fits with the behavior expected from the carrier localization
effect in the ac regime, indicates that the plateau structure, although not
quantized, still exists in the terahertz regime.Comment: 4 pages, 4 figure
Laughlin states on the Poincare half-plane and its quantum group symmetry
We find the Laughlin states of the electrons on the Poincare half-plane in
different representations. In each case we show that there exist a quantum
group symmetry such that the Laughlin states are a representation of
it. We calculate the corresponding filling factor by using the plasma analogy
of the FQHE.Comment: 9 pages,Late
The Moon at thermal infrared wavelengths: A benchmark for asteroid thermal models
Thermal-infrared measurements of asteroids are crucial for deriving the
objects' sizes, albedos, and also the thermophysical properties of the surface
material. Depending on the available data, a range of simple to complex thermal
models are applied to achieve specific science goals. However, testing these
models is often a difficult process and the uncertainties of the derived
parameters are not easy to estimate. Here, we make an attempt to verify a
widely accepted thermophysical model (TPM) against unique thermal infrared
(IR), full-disk, and well-calibrated measurements of the Moon. The data were
obtained by the High-resolution InfraRed Sounder (HIRS) instruments on board a
fleet of Earth weather satellites that serendipitously scan over the Moon. We
found 22 Moon intrusions, taken in 19 channels between 3.75 micron and 15.0
micron, and over a wide phase angle range from -73.1 deg to +73.8 deg. The
similarity between these Moon data and typical asteroid spectral-IR energy
distributions allows us to benchmark the TPM concepts and to point out
problematic aspects. The TPM predictions match the HIRS measurements within 5%
(10% at the shortest wavelengths below 5 micron when using the Moon's known
properties (size, shape, spin, albedo, thermal inertia, roughness) in
combination with a newly established wavelength-dependent hemispherical
emissivity. In the 5-7.5 micron and in the 9.5 to 11 micron ranges, the global
emissivity model deviates considerably from the known lunar sample spectra. Our
findings will influence radiometric studies of near-Earth and main-belt
asteroids in cases where only short-wavelength data (from e.g., NEOWISE, the
warm Spitzer mission, or ground-based M-band measurements) are available. The
new, full-disk IR Moon model will also be used for the calibration of IR
instrumentation on interplanetary missions (e.g., for Hayabusa-2) and weather
satellites.Comment: 21 pages, 9 figures, 7 tables, accepted for publication in Astronomy
& Astrophysics in March 202
Behaviour of three charged particles on a plane under perpendicular magnetic field
We consider the problem of three identical charged particles on a plane under
a perpendicular magnetic field and interacting through Coulomb repulsion. This
problem is treated within Taut's framework, in the limit of vanishing center of
mass vector , which corresponds to the strong magnetic
field limit, occuring for example in the Fractional Quantum Hall Effect. Using
the solutions of the biconfluent Heun equation, we compute the eigenstates and
show that there is two sets of solutions. The first one corresponds to a system
of three independent anyons which have their angular momenta fixed by the value
of the magnetic field and specified by a dimensionless parameter , the ratio of , the magnetic length, over , the Bohr
radius. This anyonic character, consistent with quantum mechanics of identical
particles in two dimensions, is induced by competing physical forces. The
second one corresponds to the case of the Landau problem when .
Finally we compare these states with the quantum Hall states and find that the
Laughlin wave functions are special cases of our solutions under certains
conditions.Comment: 15 pages, 3 figures, Accepeted in JP
Universal Multifractality in Quantum Hall Systems with Long-Range Disorder Potential
We investigate numerically the localization-delocalization transition in
quantum Hall systems with long-range disorder potential with respect to
multifractal properties. Wavefunctions at the transition energy are obtained
within the framework of the generalized Chalker--Coddington network model. We
determine the critical exponent characterizing the scaling behavior
of the local order parameter for systems with potential correlation length
up to magnetic lengths . Our results show that does not
depend on the ratio . With increasing , effects due to classical
percolation only cause an increase of the microscopic length scale, whereas the
critical behavior on larger scales remains unchanged. This proves that systems
with long-range disorder belong to the same universality class as those with
short-range disorder.Comment: 4 pages, 2 figures, postsript, uuencoded, gz-compresse
Causal Perturbation Theory and Differential Renormalization
In Causal Perturbation Theory the process of renormalization is precisely
equivalent to the extension of time ordered distributions to coincident points.
This is achieved by a modified Taylor subtraction on the corresponding test
functions. I show that the pullback of this operation to the distributions
yields expressions known from Differential Renormalization. The subtraction is
equivalent to BPHZ subtraction in momentum space. Some examples from Euclidean
scalar field theory in flat and curved spacetime will be presented.Comment: 15 pages, AMS-LaTeX, feynm
Assessing and countering reaction attacks against post-quantum public-key cryptosystems based on QC-LDPC codes
Code-based public-key cryptosystems based on QC-LDPC and QC-MDPC codes are
promising post-quantum candidates to replace quantum vulnerable classical
alternatives. However, a new type of attacks based on Bob's reactions have
recently been introduced and appear to significantly reduce the length of the
life of any keypair used in these systems. In this paper we estimate the
complexity of all known reaction attacks against QC-LDPC and QC-MDPC code-based
variants of the McEliece cryptosystem. We also show how the structure of the
secret key and, in particular, the secret code rate affect the complexity of
these attacks. It follows from our results that QC-LDPC code-based systems can
indeed withstand reaction attacks, on condition that some specific decoding
algorithms are used and the secret code has a sufficiently high rate.Comment: 21 pages, 2 figures, to be presented at CANS 201
Analysis of reaction and timing attacks against cryptosystems based on sparse parity-check codes
In this paper we study reaction and timing attacks against cryptosystems
based on sparse parity-check codes, which encompass low-density parity-check
(LDPC) codes and moderate-density parity-check (MDPC) codes. We show that the
feasibility of these attacks is not strictly associated to the quasi-cyclic
(QC) structure of the code but is related to the intrinsically probabilistic
decoding of any sparse parity-check code. So, these attacks not only work
against QC codes, but can be generalized to broader classes of codes. We
provide a novel algorithm that, in the case of a QC code, allows recovering a
larger amount of information than that retrievable through existing attacks and
we use this algorithm to characterize new side-channel information leakages. We
devise a theoretical model for the decoder that describes and justifies our
results. Numerical simulations are provided that confirm the effectiveness of
our approach
One-dimensional quantum chaos: Explicitly solvable cases
We present quantum graphs with remarkably regular spectral characteristics.
We call them {\it regular quantum graphs}. Although regular quantum graphs are
strongly chaotic in the classical limit, their quantum spectra are explicitly
solvable in terms of periodic orbits. We present analytical solutions for the
spectrum of regular quantum graphs in the form of explicit and exact periodic
orbit expansions for each individual energy level.Comment: 9 pages and 4 figure
Coulomb gas representation of quantum Hall effect on Riemann surfaces
Using the correlation function of chiral vertex operators of the Coulomb gas
model, we find the Laughlin wavefunctions of quantum Hall effect, with filling
factor , on Riemann sufaces with Poincare metric. The same is done
for quasihole wavefunctions. We also discuss their plasma analogy.Comment: 10 pages, LaTex, the paper is completely rewritten, It will be
appeared in : Jour. Phys. A 32 (1999
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