1,888 research outputs found
Test Experiment for Time-Reversal Symmetry Breaking Superconductivity
A new experiment is proposed to probe the time-reversal symmetry of a
superconductor. It is shown that a time-reversal symmetry breaking
superconductor can be identified by the observation of a fractional flux in
connection with a Josephson junction in a special geometry.Comment: 4 pages, 2 figures available upon request, Revtex, MIT-CMT-OC
Using The Censored Gamma Distribution for Modeling Fractional Response Variables with an Application to Loss Given Default
Regression models for limited continuous dependent variables having a
non-negligible probability of attaining exactly their limits are presented. The
models differ in the number of parameters and in their flexibility. Fractional
data being a special case of limited dependent data, the models also apply to
variables that are a fraction or a proportion. It is shown how to fit these
models and they are applied to a Loss Given Default dataset from insurance to
which they provide a good fit
Chirality sensitive effect on surface states in chiral p-wave superconductors
We study the local density of states at the surface of a chiral p-wave
superconductor in the presence of a weak magnetic field. As a result, the
formation of low-energy Andreev bound states is either suppressed or enhanced
by an applied magnetic field, depending on its orientation with respect to the
chirality of the p-wave superconductor. Similarly, an Abrikosov vortex, which
is situated not too far from the surface, leads to a zero-energy peak of the
density of states, if its chirality is the same as that of the superconductor,
and to a gap structure for the opposite case. We explain the underlying
principle of this effect and propose a chirality sensitive test on
unconventional superconductors.Comment: 4 pages, 2 figure
A dynamic nonstationary spatio-temporal model for short term prediction of precipitation
Precipitation is a complex physical process that varies in space and time.
Predictions and interpolations at unobserved times and/or locations help to
solve important problems in many areas. In this paper, we present a
hierarchical Bayesian model for spatio-temporal data and apply it to obtain
short term predictions of rainfall. The model incorporates physical knowledge
about the underlying processes that determine rainfall, such as advection,
diffusion and convection. It is based on a temporal autoregressive convolution
with spatially colored and temporally white innovations. By linking the
advection parameter of the convolution kernel to an external wind vector, the
model is temporally nonstationary. Further, it allows for nonseparable and
anisotropic covariance structures. With the help of the Voronoi tessellation,
we construct a natural parametrization, that is, space as well as time
resolution consistent, for data lying on irregular grid points. In the
application, the statistical model combines forecasts of three other
meteorological variables obtained from a numerical weather prediction model
with past precipitation observations. The model is then used to predict
three-hourly precipitation over 24 hours. It performs better than a separable,
stationary and isotropic version, and it performs comparably to a deterministic
numerical weather prediction model for precipitation and has the advantage that
it quantifies prediction uncertainty.Comment: Published in at http://dx.doi.org/10.1214/12-AOAS564 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Fractional vortices on grain boundaries --- the case for broken time reversal symmetry in high temperature superconductors
We discuss the problem of broken time reversal symmetry near grain boundaries
in a d-wave superconductor based on a Ginzburg-Landau theory. It is shown that
such a state can lead to fractional vortices on the grain boundary. Both
analytical and numerical results show the structure of this type of state.Comment: 9 pages, RevTeX, 5 postscript figures include
Braiding Majorana corner modes in a second-order topological superconductor
We propose the concept of a device based on a square-shaped sample of a
two-dimensional second-order topological helical superconductor which hosts two
zero-dimensional Majorana quasiparticles at the corners. The two zero-energy
modes rely on particle-hole symmetry (PHS) and their spacial position can be
shifted by rotating an in-plane magnetic field and tuning proximity-induced
spin-singlet pairing. We consider an adiabatic cycle performed on the
degenerate ground-state manifold and show that it realizes the braiding of the
two modes whereby they accumulate a non-trivial statistical phase within
one cycle. Alongside with the PHS-ensured operator algebra, the fractional
statistics confirms the Majorana nature of the zero-energy excitations. A
schematic design for a possible experimental implementation of such a device is
presented, which could be a step towards realizing non-Abelian braiding.Comment: A different physical system is considered in this version
(topological superconductor), however, the topological and symmetry features
are closely related to those of the two-layer topological insulator of
version 2 (arXiv:1904.07822v2). A more accurate distinction is made between
the fractional statistics of the Majorana corner states and their potential
non-Abelian propertie
Temperature Dependence of the Superfluid Density in a Noncentrosymmetric Superconductor
For a noncentrosymmetric superconductor such as CePt3Si, we consider a Cooper
pairing model with a two-component order parameter composed of spin-singlet and
spin-triplet pairing components.
We calculate the superfluid density tensor in the clean limit on the basis of
the quasiclassical theory of superconductivity.
We demonstrate that such a pairing model accounts for an experimentally
observed feature of the temperature dependence of the London penetration depth
in CePt3Si, i.e., line-node-gap behavior at low temperatures.Comment: 10 page
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