48,863 research outputs found
Baryon states with hidden charm in the extended local hidden gauge approach
The s-wave interaction of and , is studied within a unitary coupled channels scheme
with the extended local hidden gauge approach. In addition to the
Weinberg-Tomozawa term, several additional diagrams via the pion-exchange are
also taken into account as box potentials. Furthermore, in order to implement
the full coupled channels calculation, some of the box potentials which mix the
vector-baryon and pseudoscalar-baryon sectors are extended to construct the
effective transition potentials. As a result, we have observed six possible
states in several angular momenta. Four of them correspond to two pairs of
admixture states, two of - with , and two of - with . Moreover, we find a resonance which couples to
the channel and one spin degenerated bound state of
with .Comment: 24 pages, 6 figure
State-of-the-art and gaps for deep learning on limited training data in remote sensing
Deep learning usually requires big data, with respect to both volume and
variety. However, most remote sensing applications only have limited training
data, of which a small subset is labeled. Herein, we review three
state-of-the-art approaches in deep learning to combat this challenge. The
first topic is transfer learning, in which some aspects of one domain, e.g.,
features, are transferred to another domain. The next is unsupervised learning,
e.g., autoencoders, which operate on unlabeled data. The last is generative
adversarial networks, which can generate realistic looking data that can fool
the likes of both a deep learning network and human. The aim of this article is
to raise awareness of this dilemma, to direct the reader to existing work and
to highlight current gaps that need solving.Comment: arXiv admin note: text overlap with arXiv:1709.0030
Relative entropy of entanglement for certain multipartite mixed states
We prove conjectures on the relative entropy of entanglement (REE) for two
families of multipartite qubit states. Thus, analytic expressions of REE for
these families of states can be given. The first family of states are composed
of mixture of some permutation-invariant multi-qubit states. The results
generalized to multi-qudit states are also shown to hold. The second family of
states contain D\"ur's bound entangled states. Along the way, we have discussed
the relation of REE to two other measures: robustness of entanglement and
geometric measure of entanglement, slightly extending previous results.Comment: Single column, 22 pages, 9 figures, comments welcom
The X(3872) and other X,Y,Z Resonances as Hidden Charm Meson-Meson Molecules
We report on some ideas concerning the nature of the X(3872) resonance and
the need for approximately equal charged and neutral components of . Then we discuss how some hidden charm states are obtained from the
interaction between vector mesons with charm and can be associated to some of
the charmonium-like X,Y,Z states. Finally we discuss how the nature of these
states could be investigated through different types of radiative decay.Comment: Presented at the Charm2010 Workshop, Beijing, Oct. 201
Spectral properties, generation order parameters and luminosities for spin-powered X-ray pulsars
We show the spectral properties of 15 spin-powered X-ray pulsars, and the
correlation between the average power-law photon index and spin-down rate.
Generation order parameters (GOPs) based on polar-cap models are introduced to
characterize the X-ray pulsars. We calculate three definitions of generation
order parameters due to the different effects of magnetic and electric fields
on photon absorption during cascade processes, and study the relations between
the GOPs and spectral properties of X-ray pulsars. There exists a possible
correlation between the photon index and GOP in our pulsar sample. Furthermore,
we present a method due to the concept of GOPs to estimate the non-thermal
X-ray luminosity for spin-powered pulsars. Then X-ray luminosity is calculated
in the context of our polar-cap accelerator model which is well consistent with
the most observed X-ray pulsar data. The ratio between X-ray luminosity
estimated by our method and the pulsar's spin-down power is well consistent
with the feature.Comment: 20 pages, 8 figures, 1 table, revised version for the publication in
Ap
Loschmidt echo and fidelity decay near an exceptional point
Non-Hermitian classical and open quantum systems near an exceptional point
(EP) are known to undergo strong deviations in their dynamical behavior under
small perturbations or slow cycling of parameters as compared to Hermitian
systems. Such a strong sensitivity is at the heart of many interesting
phenomena and applications, such as the asymmetric breakdown of the adiabatic
theorem, enhanced sensing, non-Hermitian dynamical quantum phase transitions
and photonic catastrophe. Like for Hermitian systems, the sensitivity to
perturbations on the dynamical evolution can be captured by Loschmidt echo and
fidelity after imperfect time reversal or quench dynamics. Here we disclose a
rather counterintuitive phenomenon in certain non-Hermitian systems near an EP,
namely the deceleration (rather than acceleration) of the fidelity decay and
improved Loschmidt echo as compared to their Hermitian counterparts, despite
large (non-perturbative) deformation of the energy spectrum introduced by the
perturbations. This behavior is illustrated by considering the fidelity decay
and Loschmidt echo for the single-particle hopping dynamics on a tight-binding
lattice under an imaginary gauge field.Comment: 11 pages, 6 figures, to appear in Annalen der Physi
Particle Collisions on Stringy Black Hole Background
The collision of two particles in the background of a Sen black hole is
studied. With the equations of motion of the particles, the center-of-mass
energy is investigated when the collision takes place at the horizon of a Sen
black hole. For an extremal Sen black hole, we find that the center-of-mass
energy will be arbitrarily high with two conditions: (1) spin and (2)
one of the colliding particles has the critical angular momentum
. For a nonextremal Sen black hole, we show that, in order to
obtain an unlimited center-of-mass energy, one of the colliding particles
should have the critical angular momentum ( is
the radius of the outer horizon for a nonextremal black hole). However, a
particle with the angular momentum could not approach the
black hole from outside of the horizon through free fall, which implies that
the collision with arbitrarily high center-of-mass energy could not take place.
Thus, there is an upper bound of the center-of-mass energy for the nonextremal
black hole. We also obtain the maximal center-of-mass energy for a
near-extremal black hole and the result implies that the Planck-scale energy is
hard to be approached. Furthermore, we also consider the back-reaction effects.
The result shows that, neglecting the gravitational radiation, it has a weak
effect on the center-of-mass energy. However, we argue that the maximum allowed
center-of-mass energy will be greatly reduced to below the Planck-scale when
the gravitational radiation is included.Comment: 17 pages, 4 figures, published versio
Fractional vortices and composite domain walls in flat nanomagnets
We provide a simple explanation of complex magnetic patterns observed in
ferromagnetic nanostructures. To this end we identify elementary topological
defects in the field of magnetization: ordinary vortices in the bulk and
vortices with half-integer winding numbers confined to the edge. Domain walls
found in experiments and numerical simulations in strips and rings are
composite objects containing two or more of the elementary defects.Comment: Minor changes: updated references and fixed typo
Matrix permanent and quantum entanglement of permutation invariant states
We point out that a geometric measure of quantum entanglement is related to
the matrix permanent when restricted to permutation invariant states. This
connection allows us to interpret the permanent as an angle between vectors. By
employing a recently introduced permanent inequality by Carlen, Loss and Lieb,
we can prove explicit formulas of the geometric measure for permutation
invariant basis states in a simple way.Comment: 10 page
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