1,111 research outputs found
Density of states of a two-dimensional electron gas in a non-quantizing magnetic field
We study local density of electron states of a two-dimentional conductor with
a smooth disorder potential in a non-quantizing magnetic field, which does not
cause the standart de Haas-van Alphen oscillations. It is found, that despite
the influence of such ``classical'' magnetic field on the average electron
density of states (DOS) is negligibly small, it does produce a significant
effect on the DOS correlations. The corresponding correlation function exhibits
oscillations with the characteristic period of cyclotron quantum
.Comment: 7 pages, including 3 figure
Algebras generated by two bounded holomorphic functions
We study the closure in the Hardy space or the disk algebra of algebras
generated by two bounded functions, of which one is a finite Blaschke product.
We give necessary and sufficient conditions for density or finite codimension
of such algebras. The conditions are expressed in terms of the inner part of a
function which is explicitly derived from each pair of generators. Our results
are based on identifying z-invariant subspaces included in the closure of the
algebra. Versions of these results for the case of the disk algebra are given.Comment: 22 pages ; a number of minor mistakes have been corrected, and some
points clarified. Conditionally accepted by Journal d'Analyse Mathematiqu
Theory of microwave-induced oscillations in the magnetoconductivity of a 2D electron gas
We develop a theory of magnetooscillations in the photoconductivity of a
two-dimensional electron gas observed in recent experiments. The effect is
governed by a change of the electron distribution function induced by the
microwave radiation. We analyze a nonlinearity with respect to both the dc
field and the microwave power, as well as the temperature dependence determined
by the inelastic relaxation rate.Comment: Extended version of cond-mat/0310668. 12 pages, 4 figures. V2:
published version (minor changes, Fig. 4 corrected, references added
Analytical model for laser-assisted recombination of hydrogenic atoms
We introduce a new method that allows one to obtain an analytical cross
section for the laser-assisted electron-ion collision in a closed form. As an
example we perform a calculation for the hydrogen laser-assisted recombination.
The -matrix element for the process is constructed from an exact electron
Coulomb-Volkov wave function and an approximate laser modified hydrogen state.
An explicit expression for the field-enhancement coefficient of the process is
expressed in terms of the dimensionless parameter , where and are the electron charge
and momentum respectively, and and are the
amplitude and frequency of the laser field respectively. The simplified version
of the cross section of the process is derived and analyzed within a soft
photon approximation.Comment: 10 page
Interaction-induced oscillations of the tunneling density of states in a non-quantizing magnetic field
We study tunneling into interacting disordered two-dimensional electron gas
in a non-quantizing magnetic field, which does not cause the standard de Haas--
van Alphen oscillations. Interaction induces a new type of oscillations in the
tunneling density of states with the characteristic period of cyclotron
quantum.Comment: 4 pages, 1 .eps figure, submitted to Phys. Rev. Let
Pointwise consistency of the kriging predictor with known mean and covariance functions
This paper deals with several issues related to the pointwise consistency of
the kriging predictor when the mean and the covariance functions are known.
These questions are of general importance in the context of computer
experiments. The analysis is based on the properties of approximations in
reproducing kernel Hilbert spaces. We fix an erroneous claim of Yakowitz and
Szidarovszky (J. Multivariate Analysis, 1985) that the kriging predictor is
pointwise consistent for all continuous sample paths under some assumptions.Comment: Submitted to mODa9 (the Model-Oriented Data Analysis and Optimum
Design Conference), 14th-19th June 2010, Bertinoro, Ital
Tunneling ``zero-bias'' anomaly in the quasi-ballistic regime
For the first time, we study the tunneling density of states (DOS) of the
interacting electron gas beyond the diffusive limit. A strong correction to the
DOS persists even at electron energies exceeding the inverse transport
relaxation time, which could not be expected from the well-known
Altshuler-Aronov-Lee (AAL) theory. This correction originates from the
interference between the electron waves scattered by an impurity and by the
Friedel oscillation this impurity creates. Account for such processes also
revises the AAL formula for the DOS in the diffusive limit.Comment: 4 pages, 2 .eps figures, submitted to Phys. Rev. Let
Intersubband Electron Interaction in 1D-2D Junctions
We have shown that the electron transport through junctions of
one-dimensional and two-dimensional systems, as well as through quantum point
contacts, is considerably affected by the interaction of electrons of different
subbands. The interaction mechanism is caused by Friedel oscillations, which
are produced by electrons of the closed subbands even in smooth junctions.
Because of the interaction with these oscillations, electrons of the open
subbands experience a backscattering. The electron reflection coefficient,
which describes the backscattering, has a sharp peak at the energy equal to the
Fermi energy and may be as high as about 0.1. This result allows one to explain
a number of available experimental facts.Comment: 5 pages, 3 figure
Distinguished quantum states in a class of cosmological spacetimes and their Hadamard property
In a recent paper, we proved that a large class of spacetimes, not
necessarily homogeneous or isotropous and relevant at a cosmological level,
possesses a preferred codimension one submanifold, i.e., the past cosmological
horizon, on which it is possible to encode the information of a scalar field
theory living in the bulk. Such bulk-to-boundary reconstruction procedure
entails the identification of a preferred quasifree algebraic state for the
bulk theory, enjoying remarkable properties concerning invariance under
isometries (if any) of the bulk and energy positivity, and reducing to
well-known vacua in standard situations. In this paper, specialising to open
FRW models, we extend previously obtained results and we prove that the
preferred state is of Hadamard form, hence the backreaction on the metric is
finite and the state can be used as a starting point for renormalisation
procedures. That state could play a distinguished role in the discussion of the
evolution of scalar fluctuations of the metric, an analysis often performed in
the development of any model describing the dynamic of an early Universe which
undergoes an inflationary phase of rapid expansion in the past.Comment: 41 page
Topology of the gauge-invariant gauge field in two-color QCD
We investigate solutions to a nonlinear integral equation which has a central
role in implementing the non-Abelian Gauss's Law and in constructing
gauge-invariant quark and gluon fields. Here we concern ourselves with
solutions to this same equation that are not operator-valued, but are functions
of spatial variables and carry spatial and SU(2) indices. We obtain an
expression for the gauge-invariant gauge field in two-color QCD, define an
index that we will refer to as the ``winding number'' that characterizes it,
and show that this winding number is invariant to a small gauge transformation
of the gauge field on which our construction of the gauge-invariant gauge field
is based. We discuss the role of this gauge field in determining the winding
number of the gauge-invariant gauge field. We also show that when the winding
number of the gauge field is an integer , the gauge-invariant
gauge field manifests winding numbers that are not integers, and are
half-integers only when .Comment: 26 pages including 6 encapsulated postscript figures. Numerical
errors have been correcte
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