10,592 research outputs found
Many-body approach to infinite non-periodic systems: application to the surface of semi-infinite jellium
A method to implement the many-body Green function formalism in the GW
approximation for infinite non periodic systems is presented. It is suitable to
treat systems of known ``asymptotic'' properties which enter as boundary
conditions, while the effects of the lower symmetry are restricted to regions
of finite volume. For example, it can be applied to surfaces or localized
impurities. We illustrate the method with a study of the surface of
semi-infinite jellium. We report the dielectric function, the effective
potential and the electronic self-energy discussing the effects produced by the
screening and by the charge density profile near the surface.Comment: 11 pages, 4 figure
A longitudinal study of the bi-directional relationship between tobacco smoking and psychological distress in a community sample of young Australian women
Background. Tobacco smoking and poor mental health are both prevalent and detrimental health problems in young women. The temporal relationship between the two variables is unclear. We investigated the prospective bidirectional relationship between smoking and mental health over 13 years
Options for the ATLAS Level 2 Trigger
The high rate of interactions in future LHC experiments places stringent demands on the trigger and data acquisition systems. The first-level trigger for the ATLAS experiment is based on special-purpose processors designed to reduce the trigger rate from the 40 MHz beam-crossing rate to below 100 kHz. Higher-level triggers are required to reduce the data flow to about 100 MB/s (100 Hz with full data) for permanent storage. Processing for the second-level trigger uses data from regions of interest (RoIs) defined by the first-level trigger, whereas full event data (about 1 MB per event) is used at Level-3. The present paper presents options for the ATLAS Level-2 trigger
Correlation energies of inhomogeneous many-electron systems
We generalize the uniform-gas correlation energy formalism of Singwi, Tosi,
Land and Sjolander to the case of an arbitrary inhomogeneous many-particle
system. For jellium slabs of finite thickness with a self-consistent LDA
groundstate Kohn-Sham potential as input, our numerical results for the
correlation energy agree well with diffusion Monte Carlo results. For a helium
atom we also obtain a good correlation energy.Comment: 4 pages,1 figur
Collisionless hydrodynamics for 1D motion of inhomogeneous degenerate electron gases: equivalence of two recent descriptions
Recently I. Tokatly and O. Pankratov (''TP'', Phys. Rev. B 60, 15550 (1999))
used velocity moments of a semiclassical kinetic equation to derive a
hydrodynamic description of electron motion in a degenerate electron gas.
Independently, the present authors (Theochem 501-502, 327 (2000)) used
considerations arising from the Harmonic Potential Theorem (Phys. Rev. Lett.
73, 2244 (1994)) to generate a new form of high-frequency hydrodynamics for
inhomogeneous degenerate electron gases (HPT-N3 hydrodynamics). We show here
that TP hydrodynamics yields HPT-N3 hydrodynamics when linearized about a
Thomas-Fermi groundstate with one-dimensional spatial inhomnogeneity.Comment: 17p
Exchange and Correlation Kernels at the Resonance Frequency -- Implications for Excitation Energies in Density-Functional Theory
Specific matrix elements of exchange and correlation kernels in
time-dependent density-functional theory are computed. The knowledge of these
matrix elements not only constraints approximate time-dependent functionals,
but also allows to link different practical approaches to excited states,
either based on density-functional theory, or on many-body perturbation theory,
despite the approximations that have been performed to derive them.Comment: Submitted to Phys. Rev. Lett. (February 4, 1999). Other related
publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm
The Kohn mode for trapped Bose gases within the dielectric formalism
The presence of undamped harmonic center of mass oscillations of a weakly
interacting Bose gas in a harmonic trap is demonstrated within the dielectric
formalism for a previously introduced finite temperature approximation
including exchange. The consistency of the approximation with the Kohn theorem
is thereby demonstrated. The Kohn modes are found explicitly, generalizing an
earlier zero-temperature result found in the literature. It is shown how the
Kohn mode disappears from the single-particle spectrum, while remaining in the
density oscillation spectrum, when the temperature increases from below to
above the condensation temperature.Comment: 6 pages revte
Center of mass and relative motion in time dependent density functional theory
It is shown that the exchange-correlation part of the action functional
in time-dependent density functional theory , where
is the time-dependent density, is invariant under the
transformation to an accelerated frame of reference , where is an arbitrary
function of time. This invariance implies that the exchange-correlation
potential in the Kohn-Sham equation transforms in the following manner:
. Some of the
approximate formulas that have been proposed for satisfy this exact
transformation property, others do not. Those which transform in the correct
manner automatically satisfy the ``harmonic potential theorem", i.e. the
separation of the center of mass motion for a system of interacting particles
in the presence of a harmonic external potential. A general method to generate
functionals which possess the correct symmetry is proposed
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