6,011 research outputs found
Effects of degree distribution in mutual synchronization of neural networks
We study the effects of the degree distribution in mutual synchronization of
two-layer neural networks. We carry out three coupling strategies: large-large
coupling, random coupling, and small-small coupling. By computer simulations
and analytical methods, we find that couplings between nodes with large degree
play an important role in the synchronization. For large-large coupling, less
couplings are needed for inducing synchronization for both random and
scale-free networks. For random coupling, cutting couplings between nodes with
large degree is very efficient for preventing neural systems from
synchronization, especially when subnetworks are scale-free.Comment: 5 pages, 4 figure
Self-assembly of Nanometer-scale Magnetic Dots with Narrow Size Distributions on an Insulating Substrate
The self-assembly of iron dots on the insulating surface of NaCl(001) is
investigated experimentally and theoretically. Under proper growth conditions,
nanometer-scale magnetic iron dots with remarkably narrow size distributions
can be achieved in the absence of a wetting layer Furthermore, both the
vertical and lateral sizes of the dots can be tuned with the iron dosage
without introducing apparent size broadening, even though the clustering is
clearly in the strong coarsening regime. These observations are interpreted
using a phenomenological mean-field theory, in which a coverage-dependent
optimal dot size is selected by strain-mediated dot-dot interactions.Comment: 5 pages, 4 figure
Walks on weighted networks
We investigate the dynamics of random walks on weighted networks. Assuming
that the edge's weight and the node's strength are used as local information by
a random walker, we study two kinds of walks, weight-dependent walk and
strength-dependent walk. Exact expressions for stationary distribution and
average return time are derived and confirmed by computer simulations. We
calculate the distribution of average return time and the mean-square
displacement for two walks on the BBV networks, and find that a
weight-dependent walker can arrive at a new territory more easily than a
strength-dependent one.Comment: 4 pages, 5 figures. minor modifications. Comments and suggestions are
favored by the author
Estimate of the Hadronic Production of the Doubly Charmed Baryon under GM-VFN Scheme
Hadronic production of the doubly charmed baryon (
and ) is investigated under the general-mass
variable-flavor-number (GM-VFN) scheme. The gluon-gluon fusion mechanism and
the intrinsic charm mechanisms, i.e. via the sub-processes
,
; ,
and , , are taken into account in the investigation, where
(in color {\bf }) and (in color
{\bf 6}) are two possible -wave configurations of the doubly charmed diquark
pair inside the baryon . Numerical results for the production
at hadornic colliders LHC and TEVATRON show that both the contributions from
the doubly charmed diquark pairs and are
sizable with the assumption that the two NRQCD matrix elements are equal, and
the total contributions from the `intrinsic' charm mechanisms are bigger than
those of the gluon-gluon fusion mechanism. For the production in the region of
small transverse-momentum , the intrinsic mechanisms are dominant over the
gluon-gluon fusion mechanism and they can raise the theoretical prediction of
the by almost one order.Comment: 26 pages, 8 figure
Inconsistency of QED in the Presence of Dirac Monopoles
A precise formulation of local gauge invariance in QED is presented,
which clearly shows that the gauge coupling associated with the unphysical
longitudinal photon field is non-observable and actually has an arbitrary
value. We then re-examine the Dirac quantization condition and find that its
derivation involves solely the unphysical longitudinal coupling. Hence an
inconsistency inevitably arises in the presence of Dirac monopoles and this can
be considered as a theoretical evidence against their existence. An
alternative, independent proof of this conclusion is also presented.Comment: Extended and combined version, refinements added; 20 LaTex pages,
Published in Z. Phys. C65, pp.175-18
Tunable trade-off between quantum and classical computation via non-unitary Zeno-like dynamics
We propose and analyze a measurement-based non-unitary variant of the
continuous time Grover search algorithm. We derive tight analytical lower
bounds on its efficiency for arbitrary database sizes and measurement
parameters. We study the behaviour of the algorithm subject to Oracle errors,
and find that it outperforms the standard algorithm for several values of such
errors. Our analysis is based on deriving a non-hermitian effective description
of the algorithm, yielding also a deeper insight into components responsible
for the quantum and the classical operation of the protocol
An efficient, multiple range random walk algorithm to calculate the density of states
We present a new Monte Carlo algorithm that produces results of high accuracy
with reduced simulational effort. Independent random walks are performed
(concurrently or serially) in different, restricted ranges of energy, and the
resultant density of states is modified continuously to produce locally flat
histograms. This method permits us to directly access the free energy and
entropy, is independent of temperature, and is efficient for the study of both
1st order and 2nd order phase transitions. It should also be useful for the
study of complex systems with a rough energy landscape.Comment: 4 pages including 4 ps fig
- …