15,319 research outputs found
A Unique Method to Determine SNe Initial Explosion Energy
There are several different methods to determine the individual supernovae
(SNe) initial explosion energy, here we derive the average or typical explosion
energy of shell-type supernova remnants (SNRs) in a particular way. By solving
a group of equations pertaining to shell-type SNRs at the same stage we
obtained some physical parameters, e.g. the distance (), evolved age (),
etc.. Assuming series of different SN initial explosion energies ranging from
ergs to ergs, we derived series of distance and age
parameters with which compared already known ones. Thus the most likely value
of the SNe initial explosion energy is obtained when the deviation is least,
which equals to about ergs, in good agreement with the undertook
value.Comment: 12 pages, 6 figure
Distances to Two Galactic Supernova Remnants: G32.8-0.1 and G346.6-0.2
There are either a near kinematic distance of 5.5 kpc or a far distance of
8.8 kpc for a Galactic supernova remnant (SNR) G32.80.1 derived by using the
rotation curve of the Galaxy. Here we make sure that the remnant distance is
the farther one 8.8 kpc through solving a group of equations for the shell-type
remnants separately at the adiabatic-phase and the radiative-phase. For SNR
G346.60.2 we determine its distance also the farther one 11 kpc rather than
the nearer one 5.5 kpc.Comment: 5 pages, 3 figure
The effect of in-plane magnetic field and applied strain in quantum spin Hall systems: application to InAs/GaSb quantum wells
Motivated by the recent discovery of quantized spin Hall effect in InAs/GaSb
quantum wells\cite{du2013}\cite{xu2014}, we theoretically study the effects
of in-plane magnetic field and strain effect to the quantization of charge
conductance by using Landauer-Butikker formalism. Our theory predicts a
robustness of the conductance quantization against the magnetic field up to a
very high field of 20 tesla. We use a disordered hopping term to model the
strain and show that the strain may help the quantization of the conductance.
Relevance to the experiments will be discussed.Comment: 8 pages, 10 figures. Comments are welcome
Real-world Noisy Image Denoising: A New Benchmark
Most of previous image denoising methods focus on additive white Gaussian
noise (AWGN). However,the real-world noisy image denoising problem with the
advancing of the computer vision techiniques. In order to promote the study on
this problem while implementing the concurrent real-world image denoising
datasets, we construct a new benchmark dataset which contains comprehensive
real-world noisy images of different natural scenes. These images are captured
by different cameras under different camera settings. We evaluate the different
denoising methods on our new dataset as well as previous datasets. Extensive
experimental results demonstrate that the recently proposed methods designed
specifically for realistic noise removal based on sparse or low rank theories
achieve better denoising performance and are more robust than other competing
methods, and the newly proposed dataset is more challenging. The constructed
dataset of real photographs is publicly available at
\url{https://github.com/csjunxu/PolyUDataset} for researchers to investigate
new real-world image denoising methods. We will add more analysis on the noise
statistics in the real photographs of our new dataset in the next version of
this article.Comment: 13 pages, 8 figures, 8 tables. arXiv admin note: text overlap with
arXiv:1707.01313 by other author
Waiting times and stopping probabilities for patterns in Markov chains
Suppose that is a finite collection of patterns. Observe a
Markov chain until one of the patterns in occurs as a run. This
time is denoted by . In this paper, we aim to give an easy way to
calculate the mean waiting time and the stopping probabilities
with , where is the waiting time
until the pattern appears as a run.Comment: 13 page
Exact Solution to Haldane-BCS-Hubbard Model Along the Symmetric Lines: Interaction Induced Topological Phase Transition
We propose a Haldane-BCS-Hubbard model on a honeycomb lattice, which is
composed of two copies of the Haldane model of the quantum anomalous Hall
effect, an equal-spin pairing term and an onsite Hubbard interaction term. For
any interaction strength, this model is exactly solvable along the symmetric
line where the hopping and pairing amplitudes are equal to each other. The
ground state of the Haldane-BCS-Hubbard model is a topological superconducting
state at weak interaction with two chiral Majorana edge states. A strong
interaction drives the system across a topological quantum phase transition to
a topologically trivial superconductor. A symmetry of the
Hamiltonian, which is a composition of the bond-centered inversion and a gauge
transformation, is spontaneously broken by the interaction, resulting a finite
antiferromagnetic order in the -direction.Comment: 9 pages, 7 figure
Theory for Spin Selective Andreev Reflection in Vortex Core of Topological Superconductor: Majorana Zero Modes on Spherical Surface and Application to Spin Polarized Scanning Tunneling Microscope Probe
Majorana zero modes (MZMs) have been predicted to exist in the topological
insulator (TI)/superconductor (SC) heterostructure. Recent spin polarized
scanning tunneling microscope (STM) experiment has observed
spin-polarization dependence of the zero bias differential tunneling
conductance at the center of vortex core, which may be attributed to the spin
selective Andreev reflection, a novel property of the MZMs theoretically
predicted in 1-dimensional nanowire. Here we consider a helical electron
system described by a Rashba spin orbit coupling Hamiltonian on a spherical
surface with a s-wave superconducting pairing due to proximity effect. We
examine in-gap excitations of a pair of vortices with one at the north pole and
the other at the south pole. While the MZM is not a spin eigenstate, the spin
wavefunction of the MZM at the center of the vortex core, r = 0, is parallel to
the magnetic field, and the local Andreev reflection of the MZM is spin
selective, namely occurs only when the STM tip has the spin polarization
parallel to the magnetic field, similar to the case in 1-dimensional nanowire2.
The total local differential tunneling conductance consists of the normal term
proportional to the local density of states and an additional term arising from
the Andreev reflection. We also discuss the finite size effect, for which the
MZM at the north pole is hybridized with the MZM at the south pole. We apply
our theory to examine the recently reported spin-polarized STM experiments and
show good agreement with the experiments.Comment: 14 pages, 14 figures, 1 table. Comments are welcome
Orbital Feshbach Resonance: A "Wide" Narrow Resonance for Higher Transition Temperature Fermi Superfluid
In this letter we show that the recently theoretically predicted and
experimentally observed "orbital Feshbach resonance" in alkali-earth-like
Yb-173 atom is a narrow resonance in energy, while it is hundreds Gauss wide in
term of magnetic field strength, taking the advantage that the magnetic moment
difference between the open and closed channels is quite small. Therefore this
is an ideal platform for the experimental realization of a strongly interacting
Fermi superfluid with narrow resonance. We show that the transition temperature
for the Fermi superfluid in this system, especially at the BCS side of the
resonance, is even higher than that in a wide resonance, which is also due to
the narrow character of this resonance. Our results will encourage experimental
efforts to realize Fermi superfluid in the alkali-earth-like Yb-173 system, the
properties of which will be complementary to extensively studied Fermi
superfluids nearby a wide resonance in alkali K-40 and Li-6 systems.Comment: 10 pages, 5 figure
Codebook-Based Beam Tracking for Conformal ArrayEnabled UAV MmWave Networks
Millimeter wave (mmWave) communications can potentially meet the high
data-rate requirements of unmanned aerial vehicle (UAV) networks. However, as
the prerequisite of mmWave communications, the narrow directional beam tracking
is very challenging because of the three-dimensional (3D) mobility and attitude
variation of UAVs. Aiming to address the beam tracking difficulties, we propose
to integrate the conformal array (CA) with the surface of each UAV, which
enables the full spatial coverage and the agile beam tracking in highly dynamic
UAV mmWave networks. More specifically, the key contributions of our work are
three-fold. 1) A new mmWave beam tracking framework is established for the
CA-enabled UAV mmWave network. 2) A specialized hierarchical codebook is
constructed to drive the directional radiating element (DRE)-covered
cylindrical conformal array (CCA), which contains both the angular beam pattern
and the subarray pattern to fully utilize the potential of the CA. 3) A
codebook-based multiuser beam tracking scheme is proposed, where the Gaussian
process machine learning enabled UAV position/attitude predication is developed
to improve the beam tracking efficiency in conjunction with the tracking-error
aware adaptive beamwidth control. Simulation results validate the effectiveness
of the proposed codebook-based beam tracking scheme in the CA-enabled UAV
mmWave network, and demonstrate the advantages of CA over the conventional
planner array in terms of spectrum efficiency and outage probability in the
highly dynamic scenarios
Engineering of nonclassical motional states in optomechanical systems
We propose to synthesize arbitrary nonclassical motional states in
optomechanical systems by using sideband excitations and photon blockade. We
first demonstrate that the Hamiltonian of the optomechanical systems can be
reduced, in the strong single-photon optomechanical coupling regime when the
photon blockade occurs, to one describing the interaction between a driven
two-level trapped ion and the vibrating modes, and then show a method to
generate target states by using a series of classical pulses with desired
frequencies, phases, and durations. We further analyze the effect of the photon
leakage, due to small anharmonicity, on the fidelity of the expected motional
state, and study environment induced decoherence. Moreover, we also discuss the
experimental feasibility and provide operational parameters using the possible
experimental data.Comment: 11 pages, 4 figure
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