111,497 research outputs found
Sparse Distributed Learning Based on Diffusion Adaptation
This article proposes diffusion LMS strategies for distributed estimation
over adaptive networks that are able to exploit sparsity in the underlying
system model. The approach relies on convex regularization, common in
compressive sensing, to enhance the detection of sparsity via a diffusive
process over the network. The resulting algorithms endow networks with learning
abilities and allow them to learn the sparse structure from the incoming data
in real-time, and also to track variations in the sparsity of the model. We
provide convergence and mean-square performance analysis of the proposed method
and show under what conditions it outperforms the unregularized diffusion
version. We also show how to adaptively select the regularization parameter.
Simulation results illustrate the advantage of the proposed filters for sparse
data recovery.Comment: to appear in IEEE Trans. on Signal Processing, 201
Complex Monge-Amp\`ere equations on quasi-projective varieties
We introduce generalized Monge-Amp\`ere capacities and use these to study
complex Monge-Amp\`ere equations whose right-hand side is smooth outside a
divisor. We prove, in many cases, that there exists a unique normalized
solution which is smooth outside the divisor
Probing the symmetry energy at high baryon density with heavy ion collisions
The nuclear symmetry energy at densities above saturation density
() is poorly constrained theoretically and very few
relevant experimental data exist. Its study is possible through Heavy Ion
Collisions (HIC) at energies MeV, particularly with beams of
neutron-rich radioactive nuclei. The energy range implies that the momentum
dependence of the isospin fields, i.e. the difference of the effective masses
on protons and neutrons, also has to be investigated before a safe constraint
on \esy(\rho) is possible. We discuss the several observables which have been
suggested, like emission and their collective flows and the ratio of
meson yields with different isospin projection, and . We
point out several physical mechanisms that should be included in the
theoretical models to allow a direct comparison to the more precise experiments
which will be able to distinguish the isospin projection of the detected
particles: CSR/Lanzhou, FAIR/GSI, RIBF/RIKEN, FRIB/MSU.Comment: 12 opages, 5 figures, Proceedings of IWND09 - 22-25 August 2009
Shanghai (China
Isospin Distillation with Radial Flow: a Test of the Nuclear Symmetry Energy
We discuss mechanisms related to isospin transport in central collisions
between neutron-rich systems at Fermi energies. A fully consistent study of the
isospin distillation and expansion dynamics in two-component systems is
presented in the framework of a stochastic transport theory. We analyze
correlations between fragment observables, focusing on the study of the average
N/Z of fragments, as a function of their kinetic energy. We identify an
EOS-dependent relation between these observables, allowing to better
characterize the fragmentation path and to access new information on the low
density behavior of the symmetry energy.Comment: 4 pages, 4 figures (revtex4
DSMC-LBM mapping scheme for rarefied and non-rarefied gas flows
We present the formulation of a kinetic mapping scheme between the Direct
Simulation Monte Carlo (DSMC) and the Lattice Boltzmann Method (LBM) which is
at the basis of the hybrid model used to couple the two methods in view of
efficiently and accurately simulate isothermal flows characterized by variable
rarefaction effects. Owing to the kinetic nature of the LBM, the procedure we
propose ensures to accurately couple DSMC and LBM at a larger Kn number than
usually done in traditional hybrid DSMC-Navier-Stokes equation models. We show
the main steps of the mapping algorithm and illustrate details of the
implementation. Good agreement is found between the moments of the single
particle distribution function as obtained from the mapping scheme and from
independent LBM or DSMC simulations at the grid nodes where the coupling is
imposed. We also show results on the application of the hybrid scheme based on
a simpler mapping scheme for plane Poiseuille flow at finite Kn number.
Potential gains in the computational efficiency assured by the application of
the coupling scheme are estimated for the same flow.Comment: Submitted to Journal of Computational Scienc
On the singularity type of full mass currents in big cohomology classes
Let be a compact K\"ahler manifold and be a big cohomology
class. We prove several results about the singularity type of full mass
currents, answering a number of open questions in the field. First, we show
that the Lelong numbers and multiplier ideal sheaves of
-plurisubharmonic functions with full mass are the same as those of the
current with minimal singularities. Second, given another big and nef class
, we show the inclusion Third, we characterize big classes whose full
mass currents are "additive". Our techniques make use of a characterization of
full mass currents in terms of the envelope of their singularity type. As an
essential ingredient we also develop the theory of weak geodesics in big
cohomology classes. Numerous applications of our results to complex geometry
are also given.Comment: v2. Theorem 1.1 updated to include statement about multiplier ideal
sheaves. Several typos fixed. v3. we make our arguments independent of the
regularity results of Berman-Demaill
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