9,342 research outputs found
Interplay Between Yu-Shiba-Rusinov States and Multiple Andreev Reflections
Motivated by recent scanning tunneling microscopy experiments on single
magnetic impurities on superconducting surfaces, we present here a
comprehensive theoretical study of the interplay between Yu-Shiba-Rusinov bound
states and (multiple) Andreev reflections. Our theory is based on a combination
of an Anderson model with broken spin degeneracy and nonequilibrium Green's
function techniques that allows us to describe the electronic transport through
a magnetic impurity coupled to superconducting leads for arbitrary junction
transparency. Using this combination we are able to elucidate the different
tunneling processes that give a significant contribution to the subgap
transport. In particular, we predict the occurrence of a large variety of
Andreev reflections mediated by Yu-Shiba-Rusinov bound states that clearly
differ from the standard Andreev processes in non-magnetic systems. Moreover,
we provide concrete guidelines on how to experimentally identify the subgap
features originating from these tunneling events. Overall, our work provides
new insight into the role of the spin degree of freedom in Andreev transport
physics.Comment: 15 pages, 10 figure
The cluster of galaxies Abell 376
We present a dynamical analysis of the galaxy cluster Abell 376 based on a
set of 73 velocities, most of them measured at Pic du Midi and Haute-Provence
observatories and completed with data from the literature. Data on individual
galaxies are presented and the accuracy of the determined velocities is
discussed as well as some properties of the cluster. We obtained an improved
mean redshift value z=0.0478^{+0.005}_{-0.006} and velocity dispersion
sigma=852^{+120}_{-76}km/s. Our analysis indicates that inside a radius of
900h_{70}^{-1}kpc (15 arcmin) the cluster is well relaxed without any
remarkable feature and the X-ray emission traces fairly well the galaxy
distribution. A possible substructure is seen at 20 arcmin from the centre
towards the Southwest direction, but is not confirmed by the velocity field.
This SW clump is, however, kinematically bound to the main structure of Abell
376. A dense condensation of galaxies is detected at 46 arcmin (projected
distance 2.6h_{70}^{-1}Mpc) from the centre towards the Northwest and analysis
of the apparent luminosity distribution of its galaxies suggests that this
clump is part of the large scale structure of Abell 376. X-ray spectroscopic
analysis of ASCA data resulted in a temperature kT = 4.3+/-0.4 keV and metal
abundance Z = 0.32+/-0.08 Z_solar. The velocity dispersion corresponding to
this temperature using the T_X-sigma scaling relation is in agreement with the
measured galaxies velocities.Comment: 11 pages, 10 figures, accepted for publication in A&
Scattering at the Anderson transition: Power--law banded random matrix model
We analyze the scattering properties of a periodic one-dimensional system at
criticality represented by the so-called power-law banded random matrix model
at the metal insulator transition. We focus on the scaling of Wigner delay
times and resonance widths . We found that the typical values of
and (calculated as the geometric mean) scale with the system
size as and , where is the information dimension and is the
correlation dimension of eigenfunctions of the corresponding closed system.Comment: 6 pages, 8 figure
Testing equivalence of pure quantum states and graph states under SLOCC
A set of necessary and sufficient conditions are derived for the equivalence
of an arbitrary pure state and a graph state on n qubits under stochastic local
operations and classical communication (SLOCC), using the stabilizer formalism.
Because all stabilizer states are equivalent to a graph state by local unitary
transformations, these conditions constitute a classical algorithm for the
determination of SLOCC-equivalence of pure states and stabilizer states. This
algorithm provides a distinct advantage over the direct solution of the
SLOCC-equivalence condition for an unknown invertible local operator S, as it
usually allows for easy detection of states that are not SLOCC-equivalent to
graph states.Comment: 9 pages, to appear in International Journal of Quantum Information;
Minor typos corrected, updated references
Spectral Classification of Galaxies
We investigate the integrated spectra of a sample of 24 normal galaxies. A
principal component analysis suggests that most of the variance present in the
spectra is due to the differences in morphology of the galaxies in the sample.
We show that spectroscopic parameters extracted from the spectra, like the
amplitude of the 4000 \AA~ break or of the CN band, correlate well with Hubble
types and are useful for quantitative classification.Comment: 7 pages uuencoded compressed PostScript file. To appear in Vistas in
Astronomy, special issue on Artificial Neural Networks in Astronom
Probing the eigenfunction fractality with a stop watch
We study numerically the distribution of scattering phases
and of Wigner delay times for the power-law banded random
matrix (PBRM) model at criticality with one channel attached to it. We find
that is insensitive to the position of the channel and
undergoes a transition towards uniformity as the bandwidth of the PBRM
model increases. The inverse moments of Wigner delay times scale as
, where are the multifractal
dimensions of the eigenfunctions of the corresponding closed system and is
the system size. The latter scaling law is sensitive to the position of the
channel.Comment: 5 pages, 4 figure
Localized to extended states transition for two interacting particles in a two-dimensional random potential
We show by a numerical procedure that a short-range interaction induces
extended two-particle states in a two-dimensional random potential. Our
procedure treats the interaction as a perturbation and solve Dyson's equation
exactly in the subspace of doubly occupied sites. We consider long bars of
several widths and extract the macroscopic localization and correlation lengths
by an scaling analysis of the renormalized decay length of the bars. For ,
the critical disorder found is , and the critical
exponent . For two non-interacting particles we do not find any
transition and the localization length is roughly half the one-particle value,
as expected.Comment: 4 two-column pages, 4 eps figures, Revtex, to be published in
Europhys. Let
Capital Structure of Non-Farm Enterprises in The Gambia
The focus of this study is the capital structure of non-farm manufacturing enterprises in low income countries. The study examined the importance of different sources of financing, internal and external, in the capital structure of the firm and the factors explaining entrepreneurial behavior in using different financial contracts. The capital structure was modeled by considering a one-period world within a deterministic approach. A set of testable hypotheses derived from this model was applied to a sample of 153 micro, small and medium scale manufacturing enterprises in The Gambia. The findings of this study support the hypotheses that the characteristics of the enterprise, attributes of the entrepreneur, rates of return, interest rates, transaction costs of alternative sources of financing and the respective shares of these securities simultaneously determine the capital structure of the enterprise
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