3,323 research outputs found
Environment effects on the electric conductivity of the DNA
We present a theoretical analysis of the environment effects on charge
transport in double-stranded synthetic poly(G)-poly(C) DNA molecules attached
to two ideal leads. Coupling of the DNA to the environment results in two
effects: (i) localization of carrier functions due to the static disorder and
(ii) phonon-induced scattering of the carrier between these localized states,
resulting in hopping conductivity. A nonlinear Pauli master equation for
populations of localized states is used to describe the hopping transport and
calculate the electric current as a function of the applied bias. We
demonstrate that, although the electronic gap in the density of states shrinks
as the disorder increases, the voltage gap in the characteristics becomes
wider. Simple physical explanation of this effect is provided.Comment: 8 pages, 2 figures, to appear in J. Phys.: Condens. Matte
Photon recoil momentum in a Bose-Einstein condensate of a dilute gas
We develop a "minimal" microscopic model to describe a
two-pulse-Ramsay-interferometer-based scheme of measurement of the photon
recoil momentum in a Bose-Einstein condensate of a dilute gas [Campbell et al.,
Phys. Rev. Lett. 94, 170403 (2005)]. We exploit the truncated coupled
Maxwell-Schroedinger equations to elaborate the problem. Our approach provides
a theoretical tool to reproduce essential features of the experimental results.
Additionally, we enable to calculate the quantum-mechanical mean value of the
recoil momentum and its statistical distribution that provides a detailed
information about the recoil event.Comment: 6 pages, 4 figure
On the Exponential Decay of the n-point Correlation Functions and the Analyticity of the Pressure
The goal of this paper is to provide estimates leading to a direct proof of
the exponential decay of the n-point correlation functions for certain
unbounded models of Kac type. The methods are based on estimating higher order
derivatives of the solution of the Witten Laplacian equation on one forms
associated with the hamiltonian of the system. We also provide a formula for
the Taylor coefficients of the pressure that is suitable for a direct proof the
analyticity
Difficulties in learining the phonetics of the Chinese language, basic mistakes and means of correction
This article reviews the main difficulties Russian-speaking students encounter while studying the phonetics of the Chinese language, the mistakes that are often made by them at the beginning of learning pronunciation, as well as ways of correcting those mistakes
Anomalous optical absorption in a random system with scale-free disorder
We report on an anomalous behavior of the absorption spectrum in a
one-dimensional lattice with long-range-correlated diagonal disorder with a
power-like spectrum in the form S(k) ~ 1/k^A. These type of correlations give
rise to a phase of extended states at the band center, provided A is larger
than a critical value A_c. We show that for A < A_c the absorption spectrum is
single-peaked, while an additional peak arises when A > A_c, signalling the
occurrence of the Anderson transition. The peak is located slightly below the
low-energy mobility edge, providing a unique spectroscopic tool to monitor the
latter. We present qualitative arguments explaining this anomaly.Comment: 4 pages, 4 postscript figures, uses revtex
Nonlinear resonance reflection from and transmission through a dense glassy system built up of oriented linear Frenkel chains: two-level models
A theoretical study of the resonance optical response of assemblies of
oriented short (as compared to an optical wavelength) linear Frenkel chains is
carried out using a two-level model. We show that both transmittivity and
reflectivity of the film may behave in a bistable fashion and analyze how the
effects found depend on the film thickness and on the inhomogeneous width of
the exciton optical transition.Comment: 26 pages, 9 figure
Pauli-Villars Regularization in nonperturbative Hamiltonian approach on the Light Front
The advantage of Pauli-Villars regularization in quantum field theory
quantized on the light front is explained. Simple examples of scalar
field theory and Yukawa-type model are used. We give also an
example of nonperturbative calculation in the theory with Pauli-Villars fields,
using for that a model of anharmonic oscillator modified by inclusion of ghost
variables playing the role similar to Pauli-Villars fields.Comment: LaTeX, 10 pages, 2 figures. Article will be published in AIP
Conference Proceedings, the final publication will be available at
http://scitation.aip.org/content/aip/proceeding/aipc
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