83 research outputs found
Charging effects in quantum wires
We investigate the role of charging effects in a voltage-biased quantum wire.
Both the finite range of the Coulomb interaction and the long-ranged nature of
the Friedel oscillation imply a finite capacitance, leading to a charging
energy. While observable Coulomb blockade effects are absent for a single
impurity, they are crucial if islands are present. For a double barrier, we
give the resonance condition, fully taking into account the charging of the
island.Comment: 6 Pages RevTeX, no figures, Phys. Rev. B (in press
Transport of interacting electrons through a double barrier in quantum wires
We generalize the fermionic renormalization group method to describe
analytically transport through a double barrier structure in a one-dimensional
system. Focusing on the case of weakly interacting electrons, we investigate
thoroughly the dependence of the conductance on the strength and the shape of
the double barrier for arbitrary temperature T. Our approach allows us to
systematically analyze the contributions to renormalized scattering amplitudes
from different characteristic scales absent in the case of a single impurity,
without restricting the consideration to the model of a single resonant level.
Both a sequential resonant tunneling for high T and a resonant transmission for
T smaller than the resonance width are studied within the unified treatment of
transport through strong barriers. For weak barriers, we show that two
different regimes are possible. Moderately weak impurities may get strong due
to a renormalization by interacting electrons, so that transport is described
in terms of theory for initially strong barriers. The renormalization of very
weak impurities does not yield any peak in the transmission probability;
however, remarkably, the interaction gives rise to a sharp peak in the
conductance, provided asymmetry is not too high.Comment: 18 pages, 8 figures; figures added, references updated, extended
discussio
Spectra of complex networks
We propose a general approach to the description of spectra of complex
networks. For the spectra of networks with uncorrelated vertices (and a local
tree-like structure), exact equations are derived. These equations are
generalized to the case of networks with correlations between neighboring
vertices. The tail of the density of eigenvalues at large
is related to the behavior of the vertex degree distribution
at large . In particular, as , . We propose a simple approximation, which enables us to
calculate spectra of various graphs analytically. We analyse spectra of various
complex networks and discuss the role of vertices of low degree. We show that
spectra of locally tree-like random graphs may serve as a starting point in the
analysis of spectral properties of real-world networks, e.g., of the Internet.Comment: 10 pages, 4 figure
Accelerating units for commercial resonator LINACs model UELR-10-10S designed for radiation sterilization development and results of testing
Some specific design features of the accelerating units for LINACs model UELR-10-10S designed for radiation
sterilization and the electron beam characteristics obtained experimentally are considered.Описываются некоторые особенности конструкции ускорителей модели УЭЛР-10-10С, приводятся и обсуждаются характеристики электронного пучка, полученные экспериментально.Описуються деякі особливості конструкції прискорювачів моделі УЕЛР-10-10С, приводяться і
обговорюються характеристики електронного пучка, отримані експериментально
On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection
A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)
- …