845 research outputs found
Cooperative spontaneous emission in nonuniform media
The subject of this paper is modification of cooperative spontaneous emission
by a nonuniform medium, with nonuniform distributions of electromagnetic field.
A brief analyzis is presented and it is postulated, that if spontaneous
emission from an atom is strongly suppressed, cooperative emission with another
atom may be a preferred emission channel and counteract the suppression.Comment: The final publication is available at http://www.epj.or
Supersymmetric integrable scattering theories with unstable particles
We propose scattering matrices for N=1 supersymmetric integrable quantum
field theories in 1+1 dimensions which involve unstable particles in their
spectra. By means of the thermodynamic Bethe ansatz we analyze the ultraviolet
behaviour of some of these theories and identify the effective Virasoro central
charge of the underlying conformal field theories.Comment: 15 pages Late
On the stability of two-chunk file-sharing systems
We consider five different peer-to-peer file sharing systems with two chunks,
with the aim of finding chunk selection algorithms that have provably stable
performance with any input rate and assuming non-altruistic peers who leave the
system immediately after downloading the second chunk. We show that many
algorithms that first looked promising lead to unstable or oscillating
behavior. However, we end up with a system with desirable properties. Most of
our rigorous results concern the corresponding deterministic large system
limits, but in two simplest cases we provide proofs for the stochastic systems
also.Comment: 19 pages, 7 figure
Two-particle localization and antiresonance in disordered spin and qubit chains
We show that, in a system with defects, two-particle states may experience
destructive quantum interference, or antiresonance. It prevents an excitation
localized on a defect from decaying even where the decay is allowed by energy
conservation. The system studied is a qubit chain or an equivalent spin chain
with an anisotropic () exchange coupling in a magnetic field. The chain
has a defect with an excess on-site energy. It corresponds to a qubit with the
level spacing different from other qubits. We show that, because of the
interaction between excitations, a single defect may lead to multiple localized
states. The energy spectra and localization lengths are found for
two-excitation states. The localization of excitations facilitates the
operation of a quantum computer. Analytical results for strongly anisotropic
coupling are confirmed by numerical studies.Comment: Updated version, 13 pages, 5 figures To appear in Phys. Rev. B (2003
Density-functional embedding using a plane-wave basis
The constrained electron density method of embedding a Kohn-Sham system in a
substrate system (first described by P. Cortona, Phys. Rev. B {\bf 44}, 8454
(1991) and T.A. Wesolowski and A. Warshel, J. Phys. Chem {\bf 97}, 8050 (1993))
is applied with a plane-wave basis and both local and non-local
pseudopotentials. This method divides the electron density of the system into
substrate and embedded electron densities, the sum of which is the electron
density of the system of interest. Coupling between the substrate and embedded
systems is achieved via approximate kinetic energy functionals. Bulk aluminium
is examined as a test case for which there is a strong interaction between the
substrate and embedded systems. A number of approximations to the
kinetic-energy functional, both semi-local and non-local, are investigated. It
is found that Kohn-Sham results can be well reproduced using a non-local
kinetic energy functional, with the total energy accurate to better than 0.1 eV
per atom and good agreement between the electron densities.Comment: 11 pages, 4 figure
A novel data-driven robust framework based on machine learning and knowledge graph for disease classification
Abstract(#br)As Noncommunicable Diseases (NCDs) are affected or controlled by diverse factors such as age, regionalism, timeliness or seasonality, they are always challenging to be treated accurately, which has impacted on daily life and work of patients. Unfortunately, although a number of researchers have already made some achievements (including clinical or even computer-based) on certain diseases, current situation is eager to be improved via computer technologies such as data mining and Deep Learning. In addition, the progress of NCD research has been hampered by privacy of health and medical data. In this paper, a hierarchical idea has been proposed to study the effects of various factors on diseases, and a data-driven framework named d-DC with good extensibility is presented. d-DC is able to classify the disease according to the occupation on the premise where the disease is occurring in a certain region. During collecting data, we used a combination of personal or family medical records and traditional methods to build a data acquisition model. Not only can it realize automatic collection and replenishment of data, but it can also effectively tackle the cold start problem of the model with relatively few data effectively. The diversity of information gathering includes structured data and unstructured data (such as plain texts, images or videos), which contributes to improve the classification accuracy and new knowledge acquisition. Apart from adopting machine learning methods, d-DC has employed knowledge graph (KG) to classify diseases for the first time. The vectorization of medical texts by using knowledge embedding is a novel consideration in the classification of diseases. When results are singular, the medical expert system was proposed to address inconsistencies through knowledge bases or online experts. The results of d-DC are displayed by using a combination of KG and traditional methods, which intuitively provides a reasonable interpretation to the results (highly descriptive). Experiments show that d-DC achieved the improved accuracy than the other previous methods. Especially, a fusion method called RKRE based on both ResNet and the expert system attained an average correct proportion of 86.95%, which is a good feasibility study in the field of disease classification
Arbitrary rotation and entanglement of flux SQUID qubits
We propose a new approach for the arbitrary rotation of a three-level SQUID
qubit and describe a new strategy for the creation of coherence transfer and
entangled states between two three-level SQUID qubits. The former is succeeded
by exploring the coupled-uncoupled states of the system when irradiated with
two microwave pulses, and the latter is succeeded by placing the SQUID qubits
into a microwave cavity and used adiabatic passage methods for their
manipulation.Comment: Accepted for publication in Phys. Rev.
Critical Currents of Ideal Quantum Hall Superfluids
Filling factor bilayer electron systems in the quantum Hall regime
have an excitonic-condensate superfluid ground state when the layer separation
is less than a critical value . On a quantum Hall plateau current
injected and removed through one of the two layers drives a dissipationless
edge current that carries parallel currents, and a dissipationless bulk
supercurrent that carries opposing currents in the two layers. In this paper we
discuss the theory of finite supercurrent bilayer states, both in the presence
and in the absence of symmetry breaking inter-layer hybridization. Solutions to
the microscopic mean-field equations exist at all condensate phase winding
rates for zero and sufficiently weak hybridization strengths. We find, however,
that collective instabilities occur when the supercurrent exceeds a critical
value determined primarily by a competition between direct and exchange
inter-layer Coulomb interactions. The critical current is estimated using a
local stability criterion and varies as when approaches
from below. For large inter-layer hybridization, we find that the
critical current is limited by a soliton instability of microscopic origin.Comment: 18 RevTeX pgs, 21 eps figure
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