3,700 research outputs found
Landau's theorems for certain biharmonic mappings
Let be a harmonic mapping of the unit disk .
In this paper, the sharp coefficient estimates for bounded planar harmonic
mappings are established, the sharp coefficient estimates for normalized planar
harmonic mappings with are also provided. As their
applications, Landau's theorems for certain biharmonic mappings are provided,
which improve and refine the related results of earlier authors.Comment: 12 page
Transverse Shift in Andreev Reflection
An incoming electron is reflected back as a hole at a
normal-metal-superconductor interface, a process known as Andreev reflection.
We predict that there exists a universal transverse shift in this process due
to the effect of spin-orbit coupling in the normal metal. Particularly, using
both the scattering approach and the argument of angular momentum conservation,
we demonstrate that the shifts are pronounced for lightly-doped Weyl
semimetals, and are opposite for incoming electrons with different chirality,
generating a chirality-dependent Hall effect for the reflected holes. The
predicted shift is not limited to Weyl systems, but exists for a general
three-dimensional spin-orbit- coupled metal interfaced with a superconductor.Comment: 5 pages, 2 figure
A single-photon router based on a modulated cavity optomechanical system
We investigate the routing of a single-photon in a modulated cavity
optomechanical system, in which the cavity is driven by a strong coupling
field, and the mechanical resonator (MR) is modulated with a weak coherent
field. We show that, when there is no a weak coherent field modulating the MR,
the system cannot act as a single-photon router, since the signal will be
completely covered by the quantum and thermal noises. By introducing the weak
coherent field, we can achieve the routing of the single-photon by adjusting
the frequency of the weak coherent field, and the system can be immune to the
quantum and thermal noises.Comment: 6 pages, 4 figure
Nonreciprocal transmission and fast-slow light effects in a cavity optomechanical system
We study the nonreciprocal transmission and the fast-slow light effects in a
cavity optomechanical system, in which the cavity supports a clockwise and a
counter-clockwise circulating optical modes, both the two modes are driven
simultaneously by a strong pump field and a weak signal field. We find that
when the intrinsic photon loss of the cavity is equal to the external coupling
loss of the cavity, the system reveals a nonreciprocal transmission of the
signal fields. However, when the intrinsic photon loss is much less than the
external coupling loss, the nonreciprocity about the transmission properties
almost disappears, and the nonreciprocity is shown in the group delay
properties of the signal fields, and the system exhibits a nonreciprocal
fast-slow light propagation phenomenon.Comment: 6 pages, 5 figure
Finite Sample Analysis of the GTD Policy Evaluation Algorithms in Markov Setting
In reinforcement learning (RL) , one of the key components is policy
evaluation, which aims to estimate the value function (i.e., expected long-term
accumulated reward) of a policy. With a good policy evaluation method, the RL
algorithms will estimate the value function more accurately and find a better
policy. When the state space is large or continuous \emph{Gradient-based
Temporal Difference(GTD)} policy evaluation algorithms with linear function
approximation are widely used. Considering that the collection of the
evaluation data is both time and reward consuming, a clear understanding of the
finite sample performance of the policy evaluation algorithms is very important
to reinforcement learning. Under the assumption that data are i.i.d. generated,
previous work provided the finite sample analysis of the GTD algorithms with
constant step size by converting them into convex-concave saddle point
problems. However, it is well-known that, the data are generated from Markov
processes rather than i.i.d. in RL problems.. In this paper, in the realistic
Markov setting, we derive the finite sample bounds for the general
convex-concave saddle point problems, and hence for the GTD algorithms. We have
the following discussions based on our bounds. (1) With variants of step size,
GTD algorithms converge. (2) The convergence rate is determined by the step
size, with the mixing time of the Markov process as the coefficient. The faster
the Markov processes mix, the faster the convergence. (3) We explain that the
experience replay trick is effective by improving the mixing property of the
Markov process. To the best of our knowledge, our analysis is the first to
provide finite sample bounds for the GTD algorithms in Markov setting
Transverse shift in crossed Andreev reflection
Crossed Andreev reflection (CAR) is an intriguing effect that occurs in a
normal-superconductor-normal junction. In CAR, an incoming electron from one
terminal is coherently scattered as an outgoing hole into the other terminal.
Here, we reveal that there exists a transverse spatial shift in CAR, i.e., the
plane of CAR for the outgoing hole may have a sizable transverse shift from the
plane of incidence for the incoming electron. We explicitly demonstrate the
effect in a model system based on Weyl semimetals. We further show that the
effect is quite general and exists when the terminals have sizable spin-orbit
coupling. In addition, we find that the corresponding shift in the elastic
cotunneling process shows different behaviors, and it vanishes when the two
terminals are identical. Based on these findings, we suggest possible
experimental setups for detecting the effect, which may also offer an
alternative method for probing CAR.Comment: 10 pages, 6 figure
Centralized Information Interaction for Salient Object Detection
The U-shape structure has shown its advantage in salient object detection for
efficiently combining multi-scale features. However, most existing U-shape
based methods focused on improving the bottom-up and top-down pathways while
ignoring the connections between them. This paper shows that by centralizing
these connections, we can achieve the cross-scale information interaction among
them, hence obtaining semantically stronger and positionally more precise
features. To inspire the potential of the newly proposed strategy, we further
design a relative global calibration module that can simultaneously process
multi-scale inputs without spatial interpolation. Benefiting from the above
strategy and module, our proposed approach can aggregate features more
effectively while introducing only a few additional parameters. Our approach
can cooperate with various existing U-shape-based salient object detection
methods by substituting the connections between the bottom-up and top-down
pathways. Experimental results demonstrate that our proposed approach performs
favorably against the previous state-of-the-arts on five widely used benchmarks
with less computational complexity. The source code will be publicly available.Comment: V2 updates the evaluation results of all methods on the ECSSD dataset
(Table. 3 on Page. 8). In V1 we used the old version of ground-truths of
ECSSD, which were updated later by its authors. In V2 we use the updated ones
instead. Although the numerical evaluation scores of all methods on ECSSD in
V1 and V2 vary slightly, the overall trending is still the sam
Unconventional pairing induced anomalous transverse shift in Andreev reflection
Superconductors with unconventional pairings have been a fascinating subject
of research, for which a central issue is to explore effects that can be used
to characterize the pairing. The process of Andreev reflection--the reflection
of an electron as a hole at a normal-mental-superconductor interface by
transferring a Cooper pair into the superconductor--offers a basic mechanism to
probe the pairing through transport. Here we predict that in Andreev reflection
from unconventional superconductors, the reflected hole acquires an anomalous
spatial shift normal to the plane of incidence, arising from the unconventional
pairing. The transverse shift is sensitive to the superconducting gap
structure, exhibiting characteristic features for each pairing type, and can be
detected as voltage signals. Our work not only unveils a fundamentally new
effect but also suggests a powerful new technique capable of probing the
structure of unconventional pairings.Comment: 4 pages, 4 figure
Ground State Properties of Spin-Orbit Coupled Bose Gases for Arbitrary Interactions
We develop a field integral formalism to study spin-orbit-coupled (SOC) Bose
gases with arbitrary interspecies interaction. We identify various features
arising from the interplay of SOC and interspecies interaction, including a
roton minimum in the excitation spectrum and dual effects of SOC on
ground-state energies depending on interspecies interactions.
Counterintuitively, we find that at low interspecies interaction the SOC
stabilizes the system by suppressing the quantum depletion. We show that the
static structure factor is immune to the SOC in the phase space where
time-reversal symmetry is preserved. Furthermore, we present an alternate way
of studying phase fluctuations of the system.Comment: 5 pages, 4 figure
Constructing new pseudoscalar meson nonets with the observed , , and
Stimulated by the BESIII observation of , , and
, we try to pin down new pseudoscalar meson nonets including these
states. The analysis of mass spectra and the study of strong decays indicate
that and associated with and the predicted
kaon may form a new pseudoscalar meson nonet. In addition, more
experimental data for are necessary to determine its structure of
nonets. Then, , , , and the predicted kaon
can be grouped into another new nonet. These assignments to the
discussed pseudoscalar states can be further tested in experiment.Comment: 15 pages, 4 tables and 10 figures. More discussions added and typos
corrected. Accepted by Phys. Rev.
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