11,525 research outputs found
Mixing and non-mixing local minima of the entropy contrast for blind source separation
In this paper, both non-mixing and mixing local minima of the entropy are
analyzed from the viewpoint of blind source separation (BSS); they correspond
respectively to acceptable and spurious solutions of the BSS problem. The
contribution of this work is twofold. First, a Taylor development is used to
show that the \textit{exact} output entropy cost function has a non-mixing
minimum when this output is proportional to \textit{any} of the non-Gaussian
sources, and not only when the output is proportional to the lowest entropic
source. Second, in order to prove that mixing entropy minima exist when the
source densities are strongly multimodal, an entropy approximator is proposed.
The latter has the major advantage that an error bound can be provided. Even if
this approximator (and the associated bound) is used here in the BSS context,
it can be applied for estimating the entropy of any random variable with
multimodal density.Comment: 11 pages, 6 figures, To appear in IEEE Transactions on Information
Theor
Branching integrals and Casselman phenomenon
Let be a real semisimple Lie group, its maximal complex subgroup, and
its complexification.
It is known that all the -finite matrix elements on admit holomorphic
continuation to branching functions on having singularities at the a
prescribed divisor. We propose a geometric explanation of this phenomenon. The
note also contsins a general survey of holomorphic continuations of
infinite-dimensional representations.Comment: 13pp, an addendum is adde
Optimal household energy management and participation in ancillary services with PV production
The work presented in this paper deals with a project aiming to increase the value of photovoltaic (PV) solar production for residential application. To contribute to the development of the new functionalities for such system and the efficient control system to optimize its operation, this paper defines the possibility for the proposed system to participate to the ancillary services, particularly in active power service provider. This service of PV-based system for housing application, as it does not exist today, has led to a market design proposition in the distribution system. The mathematical model for calculating the optimal operation of system (sources, load, and the exchange power with the grid) results in a linear mix integer optimization problem where the objective is to maximize the profit obtained by participating to electricity market. The approach is illustrated in an example study case. The PV producer could benefit from its intervention on balancing market or ancillary services market despite of the impact on the profit of several kinds of uncertainty, as the intermittence of PV source.energy management ; ancillary services ; PV production ; household application
A new 130nm F.E readout chip for microstrip detectors
In the context of the Silicon tracking for a Linear Collider (SiLC) R&D
collaboration, a highly compact mixed-signal chip has been designed in 130nm
CMOS technology intended to read Silicon strip detectors for the experiments at
the future International Linear Collider. The chip includes eighty eight
channels of a full analog signal processing chain and analog to digital
conversion with the corresponding digital controls and readout channels. The
chip is 5x10mm2 where the analog implementation represents 4/5 of the total
Silicon area.Comment: 3 pages, 4 figures, LCWS08 worksho
Low-Energy Properties of a One-dimensional System of Interacting bosons with Boundaries
The ground state properties and low-lying excitations of a (quasi)
one-dimensional system of longitudinally confined interacting bosons are
studied. This is achieved by extending Haldane's harmonic-fluid description to
open boundary conditions. The boson density, one-particle density matrix, and
momentum distribution are obtained accounting for finite-size and boundary
effects. Friedel oscillations are found in the density. Finite-size scaling of
the momentum distribution at zero momentum is proposed as a method to obtain
from the experiment the exponent that governs phase correlations. The strong
correlations between bosons induced by reduced dimensionality and interactions
are displayed by a Bijl-Jastrow wave function for the ground state, which is
also derived.Comment: Final published version. Minor changes with respect to the previous
versio
Non-minimal Einstein-Yang-Mills-Higgs theory: Associated, color and color-acoustic metrics for the Wu-Yang monopole model
We discuss a non-minimal Einstein-Yang-Mills-Higgs model with uniaxial
anisotropy in the group space associated with the Higgs field. We apply this
theory to the problem of propagation of color and color-acoustic waves in the
gravitational background related to the non-minimal regular Wu-Yang monopole.Comment: 14 pages, no figure
Electrical conductivity measured in atomic carbon chains
The first electrical conductivity measurements of monoatomic carbon chains
are reported in this study. The chains were obtained by unraveling carbon atoms
from graphene ribbons while an electrical current flowed through the ribbon
and, successively, through the chain. The formation of the chains was
accompanied by a characteristic drop in the electrical conductivity. The
conductivity of carbon chains was much lower than previously predicted for
ideal chains. First-principles calculations using both density functional and
many-body perturbation theory show that strain in the chains determines the
conductivity in a decisive way. Indeed, carbon chains are always under varying
non-zero strain that transforms its atomic structure from cumulene to polyyne
configuration, thus inducing a tunable band gap. The modified electronic
structure and the characteristics of the contact to the graphitic periphery
explain the low conductivity of the locally constrained carbon chain.Comment: 21 pages, 9 figure
Exact semiclassical expansions for one-dimensional quantum oscillators
A set of rules is given for dealing with WKB expansions in the one-dimensional analytic case, whereby such expansions are not considered as approximations but as exact encodings of wave functions, thus allowing for analytic continuation with respect to whichever parameters the potential function depends on, with an exact control of small exponential effects. These rules, which include also the case when there are double turning points, are illustrated on various examples, and applied to the study of bound state or resonance spectra. In the case of simple oscillators, it is thus shown that the Rayleigh–Schrödinger series is Borel resummable, yielding the exact energy levels. In the case of the symmetrical anharmonic oscillator, one gets a simple and rigorous justification of the Zinn-Justin quantization condition, and of its solution in terms of “multi-instanton expansion
Resource-driven Substructural Defeasible Logic
Linear Logic and Defeasible Logic have been adopted to formalise different
features relevant to agents: consumption of resources, and reasoning with
exceptions. We propose a framework to combine sub-structural features,
corresponding to the consumption of resources, with defeasibility aspects, and
we discuss the design choices for the framework
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