14,498 research outputs found
The Singularities of the Wave Trace of the Basic Laplacian of a Riemannian Foliation
We apply techniques of microlocal analysis to the study of the transverse
geometry of Riemannian foliations in order to analyze spectral invariants of
the basic Laplacian acting on functions on a Riemannian foliation with a
bundle-like metric. In particular, we consider the trace of the basic wave
operator when the mean curvature form is basic. We extend the concept of basic
functions to distributions and demonstrate the existence of the basic wave
kernel. The singularities of the trace of this basic wave kernel occur at the
lengths of certain geodesic arcs which are orthogonal to the closures of the
leaves of the foliation. In cases when the foliation has regular closure, a
complete representation of the trace of the basic wave kernel can be computed
for . Otherwise, a partial trace formula over a certain set of lengths
of well-behaved geodesic arcs is obtained
A Method to Separate Stochastic and Deterministic Information from Electrocardiograms
In this work we present a new idea to develop a method to separate stochastic
and deterministic information contained in an electrocardiogram, ECG, which may
provide new sources of information with diagnostic purposes. We assume that the
ECG has information corresponding to many different processes related with the
cardiac activity as well as contamination from different sources related with
the measurement procedure and the nature of the observed system itself. The
method starts with the application of an improuved archetypal analysis to
separate the mentioned stochastic and deterministic information. From the
stochastic point of view we analyze Renyi entropies, and with respect to the
deterministic perspective we calculate the autocorrelation function and the
corresponding correlation time. We show that healthy and pathologic information
may be stochastic and/or deterministic, can be identified by different measures
and located in different parts of the ECG.Comment: 4 pages, 6 figure
Electron correlations in a C fullerene cluster: A lattice density-functional study of the Hubbard model
The ground-state properties of C fullerene clusters are determined in
the framework of the Hubbard model by using lattice density-functional theory
(LDFT) and scaling approximations to the interaction-energy functional. Results
are given for the ground-state energy, kinetic and Coulomb energies, local
magnetic moments, and charge-excitation gap, as a function of the Coulomb
repulsion and for electron or hole doping close half-band
filling (). The role of electron correlations is analyzed by
comparing the LDFT results with fully unrestricted Hartree-Fock (UHF)
calculations which take into account possible noncollinear arrangements of the
local spin-polarizations. The consequences of the spin-density-wave symmetry
breaking, often found in UHF, and the implications of this study for more
complex fullerene structures are discussed.Comment: 18 pages, 7 figures, Submitted to PR
Barotropic FRW cosmologies with a Dirac-like parameter
Using the known connection between Schroedinger-like equations and Dirac-like
equations in the supersymmetric context, we discuss an extension of FRW
barotropic cosmologies in which a Dirac mass-like parameter is introduced. New
Hubble cosmological parameters H_K(eta) depending on the Dirac-like parameter
are plotted and compared with the standard Hubble case H_0(eta). The new
H_K(eta) are complex quantities. The imaginary part is a supersymmetric way of
introducing dissipation and instabilities in the barotropic FRW hydrodynamicsComment: 7 pages, 4 figures, accepted at MPL
On the Statistical Foundations of Kaluza's Magnetohydrodynamics
The introduction of electromagnetic fields into the Boltzmann equation
following a 5D general relativistic approach is considered in order to
establish the transport equations for dilute charged fluids in the presence of
a weak electromagnetic field. The conserved 5D stress-energy tensor is
evaluated using the J\"uttner function for non-degenerate relativistic gases in
local equilibrium, and the evolution equations for the local thermodynamic
variables are established by means of relativistic kinetic theory. An outline
of the possibilities offered by the Kaluza-type approach to MHD is also
included.Comment: 10 page
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