1,201 research outputs found
Oscillatory instabilities in d.c. biased quantum dots
We consider a `quantum dot' in the Coulomb blockade regime, subject to an
arbitrarily large source-drain voltage V. When V is small, quantum dots with
odd electron occupation display the Kondo effect, giving rise to enhanced
conductance. Here we investigate the regime where V is increased beyond the
Kondo temperature and the Kondo resonance splits into two components. It is
shown that interference between them results in spontaneous oscillations of the
current through the dot. The theory predicts the appearance of ``Shapiro
steps'' in the current-voltage characteristics of an irradiated quantum dot;
these would constitute an experimental signature of the predicted effect.Comment: Four pages with embedded figure
Correlation induced switching of local spatial charge distribution in two-level system
We present theoretical investigation of spatial charge distribution in the
two-level system with strong Coulomb correlations by means of Heisenberg
equations analysis for localized states total electron filling numbers taking
into account pair correlations of local electron density. It was found that
tunneling current through nanometer scale structure with strongly coupled
localized states causes Coulomb correlations induced spatial redistribution of
localized charges. Conditions for inverse occupation of two-level system in
particular range of applied bias caused by Coulomb correlations have been
revealed. We also discuss possibility of charge manipulation in the proposed
system.Comment: 6 pages, 4 figures Submitted to JETP Letter
The profile of a narrow line after single scattering by Maxwellian electrons: relativistic corrections to the kernel of the integral kinetic equation
The frequency distribution of photons in frequency that results from single
Compton scattering of monochromatic radiation on thermal electrons is derived
in the mildly relativistic limit. Algebraic expressions are given for (1) the
photon redistribution function, K(nu,Omega -> nu',Omega'), and (2) the spectrum
produced in the case of isotropic incident radiation, P(nu -> nu'). The former
is a good approximation for electron temperatures kT_e < 25 keV and photon
energies hnu < 50 keV, and the latter is applicable when hnu(hnu/m_ec^2) < kT_e
< 25 keV, hnu < 50 keV. Both formulae can be used for describing the profiles
of X-ray and low-frequency lines upon scattering in hot, optically thin
plasmas, such as present in clusters of galaxies, in the coronae of accretion
disks in X-ray binaries and AGNs, during supernova explosions, etc. Both
formulae can also be employed as the kernels of the corresponding integral
kinetic equations (direction-dependent and isotropic) in the general problem of
Comptonization on thermal electrons. The K(nu,Omega -> nu',Omega') kernel, in
particular, is applicable to the problem of induced Compton interaction of
anisotropic low-frequency radiation of high brightness temperature with free
electrons in the vicinity of powerful radiosources and masers.
Fokker-Planck-type expansion (up to fourth order) of the integral kinetic
equation with the P(nu -> nu') kernel derived here leads to a generalization of
the Kompaneets equation. We further present (1) a simpler kernel that is
necessary and sufficient to derive the Kompaneets equation and (2) an
expression for the angular function for Compton scattering in a hot plasma,
which includes temperature and photon energy corrections to the Rayleigh
angular function.Comment: 29 pages, 17 figures, accepted for publication in ApJ, uses
emulateapj.sty, corrects misprints in previous astro-ph versio
On the Antenna Beam Shape Reconstruction Using Planet Transit
The calibration of the in-flight antenna beam shape and possible
beamdegradation is one of the most crucial tasks for the upcoming Planck
mission. We examine several effects which could significantly influence the
in-flight main beam calibration using planet transit: the problems of the
variability of the Jupiter's flux, the antenna temperature and passing of the
planets through the main beam. We estimate these effects on the antenna beam
shape calibration and calculate the limits on the main beam and far sidelobe
measurements, using observations of Jupiter and Saturn. We also discuss
possible effects of degradation of the mirror surfaces and specify
corresponding parameters which can help us to determine these effects.Comment: 10 pages, 8 figure
Thermal destruction of vessels with liquid upon heating
A new engineering technique of calculating the heating and thermal destruction of vessels containing liquid under extreme thermal loading conditions is offered. The heating of the shell and the internal vessel volume is described on the basis of the thermodynamic approach. The pressure growth in a vessel is a result of gas heating and liquid evaporation. Stresses within the shell and its destruction conditions are determined, which allows predicting the critical time of destruction upon heating. The calculation and experimental data for pressure growth inside the vessel are in good agreement
Suppression of Kondo effect in a quantum dot by external irradiation
We demonstrate that the external irradiation brings decoherence in the spin
states of the quantum dot. This effect cuts off the Kondo anomaly in
conductance even at zero temperature. We evaluate the dependence of the DC
conductance in the Kondo regime on the power of irradiation, this dependence
being determined by the decoherence.Comment: 4 pages, 1 figur
Generalizations of Yang-Mills Theory with Nonlinear Constitutive Equations
We generalize classical Yang-Mills theory by extending nonlinear constitutive
equations for Maxwell fields to non-Abelian gauge groups. Such theories may or
may not be Lagrangian. We obtain conditions on the constitutive equations
specifying the Lagrangian case, of which recently-discussed non-Abelian
Born-Infeld theories are particular examples. Some models in our class possess
nontrivial Galilean (c goes to infinity) limits; we determine when such limits
exist, and obtain them explicitly.Comment: Submitted to the Proceedings of the 3rd Symposium on Quantum Theory
and Symmetries (QTS3) 10-14 September 2003. Preprint 9 pages including
reference
Perturbative Renormalizations of Anyon Quantum Mechanics
In bosonic end perturbative calculations for quantum mechanical anyon systems
a regularization and renormalization procedure, analogous to those used in
field theory, is necessary. I examine the reliability and the physical
interpretation of the most commonly used bosonic end regularization procedures.
I then use the regularization procedure with the most transparent physical
interpretation to derive some bosonic end perturbation theory results on anyon
spectra, including a 3-anyon ground state energy.Comment: 19 pages, Plain LaTex, MIT-CTP-232
Influence of microwave fields on the electron transport through a quantum dot in the presence of a direct tunneling between leads
We consider the time-dependent electron transport through a quantum dot
coupled to two leads in the presence of the additional over-dot (bridge)
tunneling channel. By using the evolution operator method together with the
wide-band limit approximation we derived the analytical formulaes for the
quantum dot charge and current flowing in the system. The influence of the
external microwave field on the time-average quantum dot charge, the current
and the derivatives of the average current with respect to the gate and
source-drain voltages has been investigated for a wide range of parameters.Comment: 28 Pages, 11 Postscript figure
Classical phase space and statistical mechanics of identical particles
Starting from the quantum theory of identical particles, we show how to
define a classical mechanics that retains information about the quantum
statistics. We consider two examples of relevance for the quantum Hall effect:
identical particles in the lowest Landau level, and vortices in the
Chern-Simons Ginzburg-Landau model. In both cases the resulting {\em classical}
statistical mechanics is shown to be a nontrivial classical limit of Haldane's
exclusion statistics.Comment: 40 pages, Late
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