5,405 research outputs found
Relativistic symmetry breaking in light kaonic nuclei
As the experimental data from kaonic atoms and scatterings imply
that the -nucleon interaction is strongly attractive at saturation
density, there is a possibility to form -nuclear bound states or kaonic
nuclei. In this work, we investigate the ground-state properties of the light
kaonic nuclei with the relativistic mean field theory. It is found that the
strong attraction between and nucleons reshapes the scalar and vector
meson fields, leading to the remarkable enhancement of the nuclear density in
the interior of light kaonic nuclei and the manifest shift of the
single-nucleon energy spectra and magic numbers therein. As a consequence, the
pseudospin symmetry is shown to be violated together with enlarged spin-orbit
splittings in these kaonic nuclei.Comment: 15 pages, 7 figure
On compression rate of quantum autoencoders: Control design, numerical and experimental realization
Quantum autoencoders which aim at compressing quantum information in a
low-dimensional latent space lie in the heart of automatic data compression in
the field of quantum information. In this paper, we establish an upper bound of
the compression rate for a given quantum autoencoder and present a learning
control approach for training the autoencoder to achieve the maximal
compression rate. The upper bound of the compression rate is theoretically
proven using eigen-decomposition and matrix differentiation, which is
determined by the eigenvalues of the density matrix representation of the input
states. Numerical results on 2-qubit and 3-qubit systems are presented to
demonstrate how to train the quantum autoencoder to achieve the theoretically
maximal compression, and the training performance using different machine
learning algorithms is compared. Experimental results of a quantum autoencoder
using quantum optical systems are illustrated for compressing two 2-qubit
states into two 1-qubit states
White Dwarf Mass Growth in Cataclysmic Variables: Roles of Dwarf Novae
The disc instability mechanism (DIM) is widely accepted to account for the
transient behaviour of dwarf novae (DNe), which experience short outbursts
separated by long quiescence. The duty cycle (the ratio between the outburst
duration and the recurrence time) determines the amount of accreted mass by the
white dwarf (WDs) during outbursts, thus playing an important role in the
long-term binary evolution. Employing the code of Modules for Experiments in
Stellar Astrophysics, we systemically investigate the influence of the duty
cycles on the evolution of DNe and the mass growth of accreting carbon-oxygen
(CO) WDs. Our calculations show that, while the DIM can considerably influence
the accretion process, efficient WD-mass growth requires a particular range of
the duty cycle. For WDs with the initial masses of 0.6, 0.7 and 1.1 ,
these duty cycles are 0.0060.007, \,=\,0.005 and
\,=\,0.003, and the accumulated mass of the WDs can reach 0.1, 0.13 and 0.21
, respectively. In all of our simulations, no CO WDs can grow their
masses to the explosion mass of Type Ia supernovae of about .
Because of a much short timescale of the outburst state, the final donor-star
masses and orbital periods are insensitive to the duty cycles. Therefore, we
propose that the DIM in DNe could alleviate the WD mass problem to some extent.Comment: 9 pages, 6 figures, 4 tables. Published in MNRA
Comparative study of tapered versus conventional cylindrical balloon for stent implantation in stenotic tapered artery
The natural tapering of coronary arteries often creates a dilemma for optimal balloon sizing during stenting. The influence of different balloon types, namely, a tapered balloon and a conventional cylindrical balloon, on the mechanical performance of the stent as well as arterial mechanics was investigated via the finite element method. Stent free-expansion and stent deployment in a stenotic tapered artery were investigated numerically. The biomechanical behavior of the two balloon types was compared in terms of stent foreshortening, stent deformation, stent stress distribution, and arterial wall stress distribution. Results indicate that balloon types affect the transient behavior of the stent and the arterial mechanics. Specifically, a tapered balloon could maintain the natural tapering of the coronary artery after stent expansion. In contrast to a cylindrical balloon, tapered balloon also mitigated the foreshortening of the stent (7.69%) as well as the stress concentration in the stent and artery (8.61% and 4.17%, respectively). Hence, tapered balloons should be used in tapered arteries as they may result in low risk of artery injury. This study might provide insights for improved balloon choice and presurgical planning
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