21,930 research outputs found
Isovector spin-singlet (T=1, S=0) and isoscalar spin-triplet (T=0, S=1) pairing interactions and spin-isospin response
We review several experimental and theoretical advances that emphasise common
aspects of the study of T=1 and T=0 pairing correlations in nuclei. We first
discuss several empirical evidences of the special role played by the T=1
pairing interaction. In particular, we show the peculiar features of the
nuclear pairing interaction in the low density regime, and possible outcomes
such as the BCS-BEC crossover in nuclear matter and, in an analogous way, in
loosely bound nuclei. We then move to the competition between T=1 and T=0
pairing correlations. The effect of such competition on the low-lying spectra
is studied in N=Z odd-odd nuclei by using a three-body model; it is shown that
the inversion of the 0+ and 1+ states near the ground state, and the strong
magnetic dipole transitions between them, can be considered as a clear
manifestation of strong T=0 pairing correlations in these nuclei. The effect of
T=0 pairing correlations is also quite evident if one studies charge-changing
transitions. The Gamow-Teller (GT) states in N=Z+2 nuclei are studied here by
using self-consistent HFB+QRPA calculations in which the T=0 pairing
interaction is taken into account. Strong GT states are found, near the ground
state of daughter nuclei; these are compared with available experimental data
from charge-exchange reactions, and such comparison can pinpoint the value of
the strength of the T=0 interaction. Pair transfer reactions are eventually
discussed: while two-neutron transfer has been long proposed as a tool to
measure the T=1 superfluidity in the nuclear ground states, the study of
deuteron transfer is still in its infancy, despite its potential interest in
revealing effects coming from both T=1 and T=0 interactions.Comment: Paper submitted to Physica Scripta for inclusion in the Focus Issue
entitled "Focus Issue on Nuclear Structure: Celebrating the 75 Nobel Prize"
(by A. Bohr and B.R. Mottelson). arXiv admin note: text overlap with
arXiv:nucl-th/0512021 by other author
Nonuniqueness in spin-density-functional theory on lattices
In electronic many-particle systems, the mapping between densities and spin
magnetizations, {n(r), m(r)}, and potentials and magnetic fields, {v(r), B(r)},
is known to be nonunique, which has fundamental and practical implications for
spin-density-functional theory (SDFT). This paper studies the nonuniqueness
(NU) in SDFT on arbitrary lattices. Two new, non-trivial cases are discovered,
here called local saturation and global noncollinear NU, and their properties
are discussed and illustrated. In the continuum limit, only some well-known
special cases of NU survive.Comment: 4 pages, 1 figur
Quasi-particle random phase approximation with quasi-particle-vibration coupling: application to the Gamow-Teller response of the superfluid nucleus Sn
We propose a self-consistent quasi-particle random phase approximation (QRPA)
plus quasi-particle-vibration coupling (QPVC) model with Skyrme interactions to
describe the width and the line shape of giant resonances in open-shell nuclei,
in which the effect of superfluidity should be taken into account in both the
ground state and the excited states. We apply the new model to the Gamow-Teller
resonance in the superfluid nucleus Sn, including both the isoscalar
spin-triplet and the isovector spin-singlet pairing interactions. The strength
distribution in Sn is well reproduced and the underlying microscopic
mechanisms, related to QPVC and also to isoscalar pairing, are analyzed in
detail.Comment: 32 pages, 11 figures, 4 table
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Deep learning for cardiac image segmentation: A review
Deep learning has become the most widely used approach for cardiac image segmentation in recent years. In this paper, we provide a review of over 100 cardiac image segmentation papers using deep learning, which covers common imaging modalities including magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound (US) and major anatomical structures of interest (ventricles, atria and vessels). In addition, a summary of publicly available cardiac image datasets and code repositories are included to provide a base for encouraging reproducible research. Finally, we discuss the challenges and limitations with current deep learning-based approaches (scarcity of labels, model generalizability across different domains, interpretability) and suggest potential directions for future research
Improving the capacity of the ping-pong protocol
We present a quantum communication protocol which keeps all the properties of
the ping-pong protocol [Phys. Rev. Lett. 89, 187902 (2002)] but improves the
capacity doubly as the ping-pong protocol. Alice and Bob can use the variable
measurement basises in control mode to detect Eve's eavesdropping attack. In
message mode, Alice can use one unitary operations to encode two bits
information. Bob only needs to perform a Bell type measurement to decode
Alice's information. A classical message authentification method can protect
this protocol against the eavesdropping hiding in the quantum channel losses
and the denial-of-service (DoS) attack.Comment: 3page; PACS:03.67.Hk, 03.65.U
Existence problem of proton semi-bubble structure in the state of Si
The fully self-consistent Hartree-Fock (HF) plus random phase approximation
(RPA) based on Skyrme-type interaction is used to study the existence problem
of proton semi-bubble structure in the state of Si. The
experimental excitation energy and the B(E2) strength of the state in
Si can be reproduced quite well. The tensor effect is also studied. It
is shown that the tensor interaction has a notable impact on the excitation
energy of the state and a small effect on the B(E2) value. Besides, its
effect on the density distributions in the ground and state of
Si is negligible. Our present results with T36 and T44 show that the
state of Si is mainly caused by proton transiton from orbit to orbit, and the existence of a proton
semi-bubble structure in this state is very unlikely.Comment: 6 pages, 3 figures, 3 table
Luxury retailers’ entry and expansion strategies in China
Purpose
The purpose of this paper is to examine internationalising luxury fashion retailers’ entry and post-entry expansion strategies in mainland China.
Design/methodology/approach
The study adopts a pragmatic mixed-methods research approach, including a quantitative mail survey and qualitative face-to-face in-depth executive interviews.
Findings
Different from initial single entry methods, multiple methods are increasingly popular for luxury fashion retailers’ post-entry expansion in mainland China. Although directly controlled expansion strategies have become significant, local partnerships are still important and omnichannel distribution strategies are rapidly growing.
Research limitations/implications
The findings were generated in mainland China only.
Originality/value
This work provides an understanding of luxury fashion retailers’ activities in the Chinese market from both macro and micro perspectives. It examines luxury fashion retailers’ initial entry strategies, as well as their post-entry expansion strategies in mainland China. Few studies in the area of international luxury fashion retailing have employed a mixed-methods approach with this number of participants
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