378 research outputs found
Fermi-Edge Resonance and Tunneling in Nonequilibrium Electron Gas
Fermi-edge singularity changes in a dramatic way in a nonequilibrium system,
acquiring features which reflect the structure of energy distribution. In
particular, it splits into several components if the energy distribution
exhibits multiple steps. While conventional approaches, such as bosonization,
fail to describe the nonequilibrium problem, an exact solution for a generic
energy distribution can be obtained with the help of the method of functional
determinants. In the case of a split Fermi distribution, while the `open loop'
contribution to Green's function has power law singularities, the tunneling
density of states profile exhibits broadened peaks centered at Fermi
sub-levels.Comment: 5 pages, 1 figur
A thick shell Casimir effect
We consider the Casimir energy of a thick dielectric-diamagnetic shell under
a uniform velocity light condition, as a function of the radii and the
permeabilities. We show that there is a range of parameters in which the stress
on the outer shell is inward, and a range where the stress on the outer shell
is outward. We examine the possibility of obtaining an energetically stable
configuration of a thick shell made of a material with a fixed volume
Casimir Energy for a Purely Dielectric Cylinder by the Mode Summation Method
We use the mode summation method together with zeta-function regularization
to compute the Casimir energy of a dilute dielectric cylinder. The method is
very transparent, and sheds light on the reason the resulting energy vanishes.Comment: 11 pages, REVTeX, no figure
Computer program for determining mass properties of a rigid structure
A computer program was developed for the rapid computation of the mass properties of complex structural systems. The program uses rigid body analyses and permits differences in structural material throughout the total system. It is based on the premise that complex systems can be adequately described by a combination of basic elemental shapes. Simple geometric data describing size and location of each element and the respective material density or weight of each element were the only required input data. From this minimum input, the program yields system weight, center of gravity, moments of inertia and products of inertia with respect to mutually perpendicular axes through the system center of gravity. The program also yields mass properties of the individual shapes relative to component axes
Tunable Fermi-Edge Resonance in an Open Quantum Dot
Resonant tunneling in an open mesoscopic quantum dot is proposed as a vehicle
to realize a tunable Fermi-edge resonance with variable coupling strength. We
solve the x-ray edge problem for a generic nonseparable scatterer and apply it
to describe tunneling in a quantum dot. The tunneling current power law
exponent is linked to the S-matrix of the dot. The control of scattering by
varying the dot shape and coupling to the leads allows to explore a wide range
of exponents. Transport properties, such as weak localization, mesoscopic
conductance fluctuations, and sensitivity to Wigner-Dyson ensemble type, have
their replicas in the Fermi-edge singularity.Comment: 4 pages, 3 figure
Photon Green's function and the Casimir energy in a medium
A new expansion is established for the Green's function of the
electromagnetic field in a medium with arbitrary and . The
obtained Born series are shown to consist of two types of interactions - the
usual terms (denoted ) that appear in the Lifshitz theory combined with
a new kind of terms (which we denote by ) associated with the changes
in the permeability of the medium. Within this framework the case of uniform
velocity of light () is studied. We obtain expressions
for the Casimir energy density and the first non-vanishing contribution is
manipulated to a simplified form. For (arbitrary) spherically symmetric
we obtain a simple expression for the electromagnetic energy density, and as an
example we obtain from it the Casimir energy of a dielectric-diamagnetic ball.
It seems that the technique presented can be applied to a variety of problems
directly, without expanding the eigenmodes of the problem and using boundary
condition considerations
Factorization of quantum charge transport for non-interacting fermions
We show that the statistics of the charge transfer of non-interacting
fermions through a two-lead contact is generalized binomial, at any temperature
and for any form of the scattering matrix: an arbitrary charge-transfer process
can be decomposed into independent single-particle events. This result
generalizes previous studies of adiabatic pumping at zero temperature and of
transport induced by bias voltage.Comment: 13 pages, 3 figures, typos corrected, references adde
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