25,430 research outputs found
The effects of k-dependent self-energy in the electronic structure of correlated materials
It is known from self-energy calculations in the electron gas and sp
materials based on the GW approximation that a typical quasiparticle
renormalization factor (Z factor) is approximately 0.7-0.8. Band narrowing in
electron gas at rs = 4 due to correlation effects, however, is only
approximately 10%, significantly smaller than the Z factor would suggest. The
band narrowing is determined by the frequency-dependent self-energy, giving the
Z factor, and the momentum-dependent or nonlocal self-energy. The results for
the electron gas point to a strong cancellation between the effects of
frequency- and momentum-dependent self-energy. It is often assumed that for
systems with a nar- row band the self-energy is local. In this work we show
that even for narrow-band materials, such as SrVO3, the nonlocal self-energy is
important.Comment: 7 pages, 6 figure
Controlled Shock Shells and Intracluster Fusion Reactions in the Explosion of Large Clusters
The ion phase-space dynamics in the Coulomb explosion of very large ( atoms) deuterium clusters can be tailored using two consecutive
laser pulses with different intensities and an appropriate time delay. For
suitable sets of laser parameters (intensities and delay), large-scale shock
shells form during the explosion, thus highly increasing the probability of
fusion reactions within the single exploding clusters. In order to analyze the
ion dynamics and evaluate the intracluster reaction rate, a one-dimensional
theory is used, which approximately accounts for the electron expulsion from
the clusters. It is found that, for very large clusters (initial radius
100 nm), and optimal laser parameters, the intracluster fusion yield becomes
comparable to the intercluster fusion yield. The validity of the results is
confirmed with three-dimensional particle-in-cell simulations.Comment: 25 pages, 11 figures, to appear in Physical Review
A polarised infrared flare from Sagittarius A* and the signatures of orbiting plasma hotspots
In this article we summarise and discuss the infrared, radio, and X-ray
emission from the supermassive black hole in the Galactic Centre, SgrA*. We
include new results from near-infrared polarimetric imaging observations
obtained on May 31st, 2006. In that night, a strong flare in Ks band (2.08
microns) reaching top fluxes of ~16 mJy could be observed. This flare was
highly polarised (up to ~40%) and showed clear sub-structure on a time scale of
15 minutes, including a swing in the polarisation angle of about 70 degrees.
For the first time we were able to observe both polarised flux and short-time
variability, with high significance in the same flare event. This result adds
decisive information to the puzzle of the SgrA* activity. The observed
polarisation angle during the flare peak is the same as observed in two events
in 2004 and 2005. Our observations strongly support the dynamical emission
model of a decaying plasma hotspot orbiting SgrA* on a relativistic orbit. The
observed polarisation parameters and their variability with time might allow to
constrain the orientation of accretion disc and spin axis with respect to the
Galaxy.Comment: 9 pages, 8 figures, accepted for publication in MNRA
Embedded Electricity Quality Analyzer
Electric installations are traditionally designed for supplying an electric service. The only one associated instrument is the energy meter that is introduced only for measure the total amount of energy that will be charged to the user. However, the exploration of parameters associated with electricity can provide several advantages such the household performance devices, legal issues and later one a more sustainable way to use the electricity energy. This work presents the principle of a low cost energy analyzer that will be part of an electric home installation. Electric parameters are measured and then transmitted via Wi-Fi to a domestic server where all data are stored. This data exploitation can be later one used for several purposes, since electric efficiency to electric charges prediction.info:eu-repo/semantics/publishedVersio
Dynamics and control of the expansion of finite-size plasmas produced in ultraintense laser-matter interactions
The strong influence of the electron dynamics provides the possibility of
controlling the expansion of laser-produced plasmas by appropriately shaping
the laser pulse. A simple irradiation scheme is proposed to tailor the
explosion of large deuterium clusters, inducing the formation of shock
structures, capable of driving nuclear fusion reactions. Such a scenario has
been thoroughly investigated, resorting to two- and three-dimensional
particle-in-cell simulations. Furthermore, the intricate dynamics of ions and
electrons during the collisionless expansion of spherical nanoplasmas has been
analyzed in detail using a self-consistent ergodic-kinetic model. This study
clarifies the transition from hydrodynamic-like to Coulomb-explosion regimes
Massive binaries in the vicinity of Sgr A*
A long-term spectroscopic and photometric survey of the most luminous and
massive stars in the vicinity of the super-massive black hole Sgr A* revealed
two new binaries; a long-period Ofpe/WN9 binary, GCIRS 16NE, with a modest
eccentricity of 0.3 and a period of 224 days and an eclipsing Wolf-Rayet binary
with a period of 2.3 days. Together with the already identified binary GCIRS
16SW, there are now three confirmed OB/WR binaries in the inner 0.2\,pc of the
Galactic Center. Using radial velocity change upper limits, we were able to
constrain the spectroscopic binary fraction in the Galactic Center to at a confidence level of 95%, a massive binary
fraction similar to that observed in dense clusters. The fraction of eclipsing
binaries with photometric amplitudes is , which is consistent with local OB star clusters ().
Overall the Galactic Center binary fraction seems to be close to the binary
fraction in comparable young clusters.Comment: 5 figures, submitted to Ap
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