1,559 research outputs found
Poisson equation and self-consistent periodical Anderson model
We show that the formally exact expression for the free energy (with a
non-relativistic Hamiltonian) for the correlated metal generates the Poisson
equation within the saddle-point approximation for the electric potential,
where the charge density automatically includes correlations. In this
approximation the problem is reduced to the self-consistent periodical Anderson
model (SCPAM). The parameter of the mixing interaction in this formulation have
to be found self-consistently together with the correlated charge density. The
factors, calculated by Irkhin, for the mixing interaction, which reflect the
structure of the many-electron states of the \f-ion involved, arise
automatically in this formulation and are quite sensitive to the specific
element we are interested in. We also discuss the definitions of the mixing
interaction for the mapping from ab initio to model calculations.Comment: 25 pages, no figure
Short wavelength quantum electrodynamical correction to cold plasma-wave propagation
The effect of short wavelength quantum electrodynamic (QED) correction on
plasma-wave propagation is investigated. The effect on plasma oscillations and
on electromagnetic waves in an unmagnetized as well as a magnetized plasma is
investigated. The effects of the short wavelength QED corrections are most
significant for plasma oscillations and for extraordinary modes. In particular,
the QED correction allow plasma oscillations to propagate, and the
extra-ordinary mode looses its stop band. The significance of our results is
discussed.Comment: 12 pages, 5 figure
Geometric phases of scattering states in a ring geometry: adiabatic pumping in mesoscopic devices
Geometric phases of scattering states in a ring geometry are studied based on
a variant of the adiabatic theorem. Three time scales, i.e., the adiabatic
period, the system time and the dwell time, associated with adiabatic
scattering in a ring geometry plays a crucial role in determining geometric
phases, in contrast to only two time scales, i.e., the adiabatic period and the
dwell time, in an open system. We derive a formula connecting the gauge
invariant geometric phases acquired by time-reversed scattering states and the
circulating (pumping) current. A numerical calculation shows that the effect of
the geometric phases is observable in a nanoscale electronic device.Comment: 9 pages, 3 figure
Trigger, an active release experiment that stimulated auroral particle precipitation and wave emissions
The experiment design, including a description of the diagnostic and chemical release payload, and the general results are given for an auroral process simulation experiment. A drastic increase of the field aligned charged particle flux was observed over the approximate energy range 10 eV to more than 300 keV, starting about 150 ms after the release and lasting about one second. The is evidence of a second particle burst, starting one second after the release and lasting for tens of seconds, and evidence for a periodic train of particle bursts occurring with a 7.7 second period from 40 to 130 seconds after the release. A transient electric field pulse of 200 mv/m appeared just before the particle flux increase started. Electrostatic wave emissions around 2 kHz, as well as a delayed perturbation of the E-region below the plasma cloud were also observed. Some of the particle observations are interpreted in terms of field aligned electrostatic acceleration a few hundred kilometers above the injected plasma cloud. It is suggested that the acceleration electric field was created by an instability driven by field aligned currents originating in the plasma cloud
A comparison of high-frequency cross-correlation measures
On a high-frequency scale the time series are not homogeneous, therefore standard correlation measures can not be directly applied to the raw data. There are two ways to deal with this problem. The time series can be homogenised through an interpolation method [1] (linear or previous tick) and then the Pearson correlation statistic computed. Recently, methods that can handle raw non-synchronous time series have been developed [2,4]. This paper compares two traditional methods that use interpolation with an alternative method applied directly to the actual time series
Superconducting single-mode contact as a microwave-activated quantum interferometer
The dynamics of a superconducting quantum point contact biased at subgap
voltages is shown to be strongly affected by a microwave electromagnetic field.
Interference among a sequence of temporally localized, microwave-induced
Landau-Zener transitions between current carrying Andreev levels results in
energy absorption and in an increase of the subgap current by several orders of
magnitude. The contact is an interferometer in the sense that the current is an
oscillatory function of the inverse bias voltage. Possible applications to
Andreev-level spectroscopy and microwave detection are discussed
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