15,328 research outputs found
Isovector channel of quark-meson-coupling model and its effect on symmetry energy
The non-relativistic approximation of the quark-meson-coupling model has been
discussed and compared with the Skyrme-Hartree-Fock model which includes spin
exchanges. Calculations show that the spin-exchange interaction has important
effect on the descriptions of finite nuclei and nuclear matter through the Fock
exchange. Also in the quark-meson-coupling model, it is the Fock exchange that
leads to a nonlinear density-dependent isovector channel and changes the
density-dependent behavior of the symmetry energy.Comment: 20 pages, 9 figures and 1 table, accepted for publication in Nuclear
Physics
Phase-Remapping Attack in Practical Quantum Key Distribution Systems
Quantum key distribution (QKD) can be used to generate secret keys between
two distant parties. Even though QKD has been proven unconditionally secure
against eavesdroppers with unlimited computation power, practical
implementations of QKD may contain loopholes that may lead to the generated
secret keys being compromised. In this paper, we propose a phase-remapping
attack targeting two practical bidirectional QKD systems (the "plug & play"
system and the Sagnac system). We showed that if the users of the systems are
unaware of our attack, the final key shared between them can be compromised in
some situations. Specifically, we showed that, in the case of the
Bennett-Brassard 1984 (BB84) protocol with ideal single-photon sources, when
the quantum bit error rate (QBER) is between 14.6% and 20%, our attack renders
the final key insecure, whereas the same range of QBER values has been proved
secure if the two users are unaware of our attack; also, we demonstrated three
situations with realistic devices where positive key rates are obtained without
the consideration of Trojan horse attacks but in fact no key can be distilled.
We remark that our attack is feasible with only current technology. Therefore,
it is very important to be aware of our attack in order to ensure absolute
security. In finding our attack, we minimize the QBER over individual
measurements described by a general POVM, which has some similarity with the
standard quantum state discrimination problem.Comment: 13 pages, 8 figure
Twenty Years of Student Scholarship: Celebrating the Dalhousie Journal of Legal Studies
In this paper, we propose a novel controllable text-to-image generative
adversarial network (ControlGAN), which can effectively synthesise high-quality
images and also control parts of the image generation according to natural
language descriptions. To achieve this, we introduce a word-level spatial and
channel-wise attention-driven generator that can disentangle different visual
attributes, and allow the model to focus on generating and manipulating
subregions corresponding to the most relevant words. Also, a word-level
discriminator is proposed to provide fine-grained supervisory feedback by
correlating words with image regions, facilitating training an effective
generator which is able to manipulate specific visual attributes without
affecting the generation of other content. Furthermore, perceptual loss is
adopted to reduce the randomness involved in the image generation, and to
encourage the generator to manipulate specific attributes required in the
modified text. Extensive experiments on benchmark datasets demonstrate that our
method outperforms existing state of the art, and is able to effectively
manipulate synthetic images using natural language descriptions. Code is
available at https://github.com/mrlibw/ControlGAN.Comment: NeurIPS 201
Alternate proof of the Rowe-Rosensteel proposition and seniority conservation
For a system with three identical nucleons in a single- shell, the states
can be written as the angular momentum coupling of a nucleon pair and the odd
nucleon. The overlaps between these non-orthonormal states form a matrix which
coincides with the one derived by Rowe and Rosensteel [Phys. Rev. Lett. {\bf
87}, 172501 (2001)]. The propositions they state are related to the eigenvalue
problems of the matrix and dimensions of the associated subspaces. In this
work, the propositions will be proven from the symmetric properties of the
symbols. Algebraic expressions for the dimension of the states, eigenenergies
as well as conditions for conservation of seniority can be derived from the
matrix.Comment: 9 pages, no figur
Determination and optimization of mode matching into optical cavities by heterodyne detection
We report on a novel high-sensitivity method to characterize and improve mode matching into optical cavities. This method is based on heterodyne detection of cylindrical transverse cavity modes. A specially designed annular-segmented photodiode is used to measure the amplitude of nonresonant modes reflected by the cavity. Our measurements allow us to optimize cavity mode matching to nearly 99.98% and will play an important diagnostic role in gravitational-wave detectors
Monotonicity and logarithmic convexity relating to the volume of the unit ball
Let stand for the volume of the unit ball in for
. In the present paper, we prove that the sequence
is logarithmically convex and that the sequence
is strictly
decreasing for . In addition, some monotonic and concave properties of
several functions relating to are extended and generalized.Comment: 12 page
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