18,299 research outputs found
Application of XFaster power spectrum and likelihood estimator to Planck
We develop the XFaster Cosmic Microwave Background (CMB) temperature and
polarization anisotropy power spectrum and likelihood technique for the Planck
CMB satellite mission. We give an overview of this estimator and its current
implementation and present the results of applying this algorithm to simulated
Planck data. We show that it can accurately extract the power spectrum of
Planck data for the high-l multipoles range. We compare the XFaster
approximation for the likelihood to other high-l likelihood approximations such
as Gaussian and Offset Lognormal and a low-l pixel-based likelihood. We show
that the XFaster likelihood is not only accurate at high-l, but also performs
well at moderately low multipoles. We also present results for cosmological
parameter Markov Chain Monte Carlo estimation with the XFaster likelihood. As
long as the low-l polarization and temperature power are properly accounted
for, e.g., by adding an adequate low-l likelihood ingredient, the input
parameters are recovered to a high level of accuracy.Comment: 25 pages, 20 figures, updated to reflect published version: slightly
extended account of XFaster technique, added improved plots and minor
corrections. Accepted for publication in MNRA
Efficient atomic self-interaction correction scheme for non-equilibrium quantum transport
Density functional theory calculations of electronic transport based on local
exchange and correlation functionals contain self-interaction errors. These
originate from the interaction of an electron with the potential generated by
itself and may be significant in metal-molecule-metal junctions due to the
localized nature of the molecular orbitals. As a consequence, insulating
molecules in weak contact with metallic electrodes erroneously form highly
conducting junctions, a failure similar to the inability of local functionals
of describing Mott-Hubbard insulators. Here we present a fully self-consistent
and still computationally undemanding self-interaction correction scheme that
overcomes these limitations. The method is implemented in the Green's function
non-equilibrium transport code Smeagol and applied to the prototypical cases of
benzene molecules sandwiched between gold electrodes. The self-interaction
corrected Kohn-Sham highest occupied molecular orbital now reproduces closely
the negative of the molecular ionization potential and is moved away from the
gold Fermi energy. This leads to a drastic reduction of the low bias current in
much better agreement with experiments.Comment: 4 pages, 5 figure
Bounds on topological Abelian string-vortex and string-cigar from information-entropic measure
In this work we obtain bounds on the topological Abelian string-vortex and on
the string-cigar, by using a new measure of configurational complexity, known
as configurational entropy. In this way, the information-theoretical measure of
six-dimensional braneworlds scenarios are capable to probe situations where the
parameters responsible for the brane thickness are arbitrary. The so-called
configurational entropy (CE) selects the best value of the parameter in the
model. This is accomplished by minimizing the CE, namely, by selecting the most
appropriate parameters in the model that correspond to the most organized
system, based upon the Shannon information theory. This information-theoretical
measure of complexity provides a complementary perspective to situations where
strictly energy-based arguments are inconclusive. We show that the higher the
energy the higher the CE, what shows an important correlation between the
energy of the a localized field configuration and its associated entropic
measure.Comment: 6 pages, 7 figures, final version to appear in Phys. Lett.
TWO-PION EXCHANGE NUCLEAR POTENTIAL - CHIRAL CANCELLATIONS
We show that chiral symmetry is responsible for large cancellations in the
two-pion exchange nucleon-nucleon interaction, which are similar to those
occuring in free pion-nucleon scattering.Comment: REVTEX style, 5 pages, 3 PostScrip figures compressed, tarred and
uuencode
False Vacuum Transitions - Analytical Solutions and Decay Rate Values
In this work we show a class of oscillating configurations for the evolution
of the domain walls in Euclidean space. The solutions are obtained
analytically. Phase transitions are achieved from the associated fluctuation
determinant, by the decay rates of the false vacuum.Comment: 6 pages, improved to match the final version to appear in EP
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