6,950 research outputs found
Large deviations for random walks under subexponentiality: the big-jump domain
For a given one-dimensional random walk with a subexponential
step-size distribution, we present a unifying theory to study the sequences
for which as
uniformly for . We also investigate the stronger "local"
analogue, . Our
theory is self-contained and fits well within classical results on domains of
(partial) attraction and local limit theory. When specialized to the most
important subclasses of subexponential distributions that have been studied in
the literature, we reproduce known theorems and we supplement them with new
results.Comment: Published in at http://dx.doi.org/10.1214/07-AOP382 the Annals of
Probability (http://www.imstat.org/aop/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Nuclear collective motion with a coherent coupling interaction between quadrupole and octupole modes
A collective Hamiltonian for the rotation-vibration motion of nuclei is
considered, in which the axial quadrupole and octupole degrees of freedom are
coupled through the centrifugal interaction. The potential of the system
depends on the two deformation variables and . The system is
considered to oscillate between positive and negative -values, by
rounding an infinite potential core in the -plane with
. By assuming a coherent contribution of the quadrupole and octupole
oscillation modes in the collective motion, the energy spectrum is derived in
an explicit analytic form, providing specific parity shift effects. On this
basis several possible ways in the evolution of quadrupole-octupole
collectivity are outlined. A particular application of the model to the energy
levels and electric transition probabilities in alternating parity spectra of
the nuclei Nd, Sm, Gd and Dy is presented.Comment: 25 pages, 13 figures. Accepted in Phys. Rev.
An evolution equation as the WKB correction in long-time asymptotics of Schrodinger dynamics
We consider 3d Schrodinger operator with long-range potential that has
short-range radial derivative. The long-time asymptotics of non-stationary
problem is studied and existence of modified wave operators is proved. It turns
out, the standard WKB correction should be replaced by the solution to certain
evolution equation.Comment: This is a preprint of an article whose final and definitive form has
been published in Comm. Partial Differential Equations, available online at
http://www.informaworld.co
Alpha-nucleus potential for alpha-decay and sub-barrier fusion
The set of parameters for alpha-nucleus potential is derived by using the
data for both the alpha-decay half-lives and the fusion cross-sections around
the barrier for reactions alpha+40Ca, alpha+59Co, alpha+208Pb. The alpha-decay
half-lives are obtained in the framework of a cluster model using the WKB
approximation. The evaluated alpha-decay half-lives and the fusion
cross-sections agreed well with the data. Fusion reactions between
alpha-particle and heavy nuclei can be used for both the formation of very
heavy nuclei and spectroscopic studies of the formed compound nuclei.Comment: 10 pages, 5 figure
Novel quantum NMR magnetometer non-contact defectoscopy and monitoring technique for the safe exploitation of gas pipelines
Pipeline transportation has already proved to be a high-performance tool of resources transportation for the efficient functioning of modern society. However, an aggressive environment, the modernization of existing pipelines and the building of new pipelines pose a number of problems to be solved for secure exploitation. Such problems include mapping, systems certification, technical inspection and monitoring. Recently much attention has being paid to the effective solution of these problems, with no interference into the functioning of the existing systems (non-contact methods), and the magnetometric technique is one such method. The method presented in this paper is based on the interpretation of the absolute value of the magnetic field of an object, which allows us to carry out measurements more accurately compared to other approaches. This paper presents the preliminary results of the usage of high-precision absolute quantum Overhauser “POS” (proton Overhauser sensor) magnetometers in the oil-and-gas field. The field work conducted in the summer of 2013 showed that this equipment has great potential for safe exploitation of oil-and-gas pipelines. The efficiency of the geophysical equipment for gas pipelines of a large diameter (1400 mm) was also confirmed under actual operating conditions. © 2014 WIT Press.International Journal of Sustainable Development and Planning;WIT Transactions on Ecology and the Environmen
Anomalous biased diffusion in a randomly layered medium
We present analytical results for the biased diffusion of particles moving
under a constant force in a randomly layered medium. The influence of this
medium on the particle dynamics is modeled by a piecewise constant random
force. The long-time behavior of the particle position is studied in the frame
of a continuous-time random walk on a semi-infinite one-dimensional lattice. We
formulate the conditions for anomalous diffusion, derive the diffusion laws and
analyze their dependence on the particle mass and the distribution of the
random force.Comment: 19 pages, 1 figur
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