97,163 research outputs found
The role of components in the N(1440) resonance
The role of 5-quark components in the pion and electromagnetic decays and
transition form factors of the N(1440) is explored. The
components, where the 4-quark subsystem has the flavor-spin symmetries
and , which are expected to have
the lowest energy of all configurations, are considered in detail
with a nonrelativistic quark model. The matrix elements between the 5-quark
components of the N(1440) and the nucleon, , play a
minor role in these decays, while the transition matrix elements and that involve quark antiquark annihilation are very
significant. Both for the electromagnetic and strong decay the change from the
valence quark model value is dominated by the confinement triggered
annihilation transitions. In the case of pion decay the calculated decay width
is enhanced substantially both by the direct and also by the
confinement triggered transitions. Agreement with the
empirical value for the pion decay width may be reached with a 30%
component in the N(1440).Comment: 23 pages revte
Five-quark components in decay
Five-quark components in the are shown to
contribute significantly to decay through
quark-antiquark annihilation transitions. These involve the overlap between the
and components and may be triggered by the confining
interaction between the quarks. With a 10% admixture of five-quark
components in the the decay width can be larger by factors 2 - 3
over that calculated in the quark model with 3 valence quarks, depending on the
details of the confining interaction. The effect of transitions between the
components themselves on the calculated decay width is however
small. The large contribution of the quark-antiquark annihilation transitions
thus may compensate the underprediction of the width of the by
the valence quark model, once the contains
components with 10% probability.Comment: accepted versio
Parameter Sensitivity Analysis of Social Spider Algorithm
Social Spider Algorithm (SSA) is a recently proposed general-purpose
real-parameter metaheuristic designed to solve global numerical optimization
problems. This work systematically benchmarks SSA on a suite of 11 functions
with different control parameters. We conduct parameter sensitivity analysis of
SSA using advanced non-parametric statistical tests to generate statistically
significant conclusion on the best performing parameter settings. The
conclusion can be adopted in future work to reduce the effort in parameter
tuning. In addition, we perform a success rate test to reveal the impact of the
control parameters on the convergence speed of the algorithm
An approximation scheme for quasi-stationary distributions of killed diffusions
In this paper we study the asymptotic behavior of the normalized weighted
empirical occupation measures of a diffusion process on a compact manifold
which is killed at a smooth rate and then regenerated at a random location,
distributed according to the weighted empirical occupation measure. We show
that the weighted occupation measures almost surely comprise an asymptotic
pseudo-trajectory for a certain deterministic measure-valued semiflow, after
suitably rescaling the time, and that with probability one they converge to the
quasi-stationary distribution of the killed diffusion. These results provide
theoretical justification for a scalable quasi-stationary Monte Carlo method
for sampling from Bayesian posterior distributions.Comment: v2: revised version, 29 pages, 1 figur
Base Station Switching Problem for Green Cellular Networks with Social Spider Algorithm
With the recent explosion in mobile data, the energy consumption and carbon
footprint of the mobile communications industry is rapidly increasing. It is
critical to develop more energy-efficient systems in order to reduce the
potential harmful effects to the environment. One potential strategy is to
switch off some of the under-utilized base stations during off-peak hours. In
this paper, we propose a binary Social Spider Algorithm to give guidelines for
selecting base stations to switch off. In our implementation, we use a penalty
function to formulate the problem and manage to bypass the large number of
constraints in the original optimization problem. We adopt several randomly
generated cellular networks for simulation and the results indicate that our
algorithm can generate superior performance
Sea-quark effects in the pion charge form factor
It is shown that the data on the pion charge form factor admit the
possibility for a substantial sea-quark components in the pion wave function.
If the charge form factor is calculated with instant form kinematics in a
constituent quark model that is extended to include explicit
components in the pion wave function, that component will give the dominant
contribution to the calculated charge form factor at large values of
momentum transfer. The present experimental values can be described well
with component admixtures of up to 50%. The sensitivity of the
calculated charge form factor to whether one of the quarks or one of
the antiquarks is taken to be in the P-state is small.Comment: 14 page
Analytical theory of dark nonlocal solitons
We investigate properties of dark solitons in nonlocal materials with an
arbitrary degree of nonlocality. We employ the variational technique and
describe the dark solitons, for the first time, in the whole range of degree of
nonlocality.Comment: to be published in Optics Letter
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