445 research outputs found
Stationary States in Bistable System Driven by L\'evy Noise
We study the properties of the probability density function (PDF) of a
bistable system driven by heavy tailed white symmetric L\'evy noise. The shape
of the stationary PDF is found analytically for the particular case of the
L\'evy index \alpha = 1 (Cauchy noise). For an arbitrary L\'evy index we employ
numerical methods based on the solution of the stochastic Langevin equation and
space fractional kinetic equation. In contrast with the bistable system driven
by Gaussian noise, in the L\'evy case the positions of maxima of the stationary
PDF do not coincide with the positions of minima of the bistable potential. We
provide a detailed study of the distance between the maxima and the minima as a
function of the potential's depth and L\'evy noise parameters.Comment: Accepted to EPJS
Meromorphic Approximants to Complex Cauchy Transforms with Polar Singularities
We study AAK-type meromorphic approximants to functions , where is a
sum of a rational function and a Cauchy transform of a complex measure
with compact regular support included in , whose argument has
bounded variation on the support. The approximation is understood in -norm
of the unit circle, . We obtain that the counting measures of poles of
the approximants converge to the Green equilibrium distribution on the support
of relative to the unit disk, that the approximants themselves
converge in capacity to , and that the poles of attract at least as many
poles of the approximants as their multiplicity and not much more.Comment: 39 pages, 4 figure
Mixing of fermion fields of opposite parities and baryon resonances
We consider a loop mixing of two fermion fields of opposite parities whereas
the parity is conserved in a Lagrangian. Such kind of mixing is specific for
fermions and has no analogy in boson case. Possible applications of this effect
may be related with physics of baryon resonances. The obtained matrix
propagator defines a pair of unitary partial amplitudes which describe the
production of resonances of spin and different parity or
. The use of our amplitudes for joint description of
partial waves and shows that the discussed effect is clearly
seen in these partial waves as the specific form of interference between
resonance and background. Another interesting application of this effect may be
a pair of partial waves and where the picture is more
complicated due to presence of several resonance states.Comment: 22 pages, 6 figures, more detailed comparison with \pi N PW
Fermion resonance in quantum field theory
We derive accurately the fermion resonance propagator by means of Dyson
summation of the self-energy contribution. It turns out that the relativistic
fermion resonance differs essentially from its boson analog.Comment: 8 pages, 2 figures, revtex4 class; references added, style
correction
Fractional Kinetics for Relaxation and Superdiffusion in Magnetic Field
We propose fractional Fokker-Planck equation for the kinetic description of
relaxation and superdiffusion processes in constant magnetic and random
electric fields. We assume that the random electric field acting on a test
charged particle is isotropic and possesses non-Gaussian Levy stable
statistics. These assumptions provide us with a straightforward possibility to
consider formation of anomalous stationary states and superdiffusion processes,
both properties are inherent to strongly non-equilibrium plasmas of solar
systems and thermonuclear devices. We solve fractional kinetic equations, study
the properties of the solution, and compare analytical results with those of
numerical simulation based on the solution of the Langevin equations with the
noise source having Levy stable probability density. We found, in particular,
that the stationary states are essentially non-Maxwellian ones and, at the
diffusion stage of relaxation, the characteristic displacement of a particle
grows superdiffusively with time and is inversely proportional to the magnetic
field.Comment: 15 pages, LaTeX, 5 figures PostScrip
Russian Manufacturing Revisited: Industrial Enterprises at the Start of the Crisis
The paper is based on the findings of a major project by the Higher School of Economics Institute for
Industrial and Market Studies (IIMS) to monitor competitiveness of manufacturing enterprises. The
study focuses on the drivers and dynamics of business competitiveness, including changes in firms’
behavior during the period before the crisis (2005-2008). The primary issue was to find out what firms
and to what extent succeeded in capitalizing on the strong economic growth before the crisis to catch
up with their competitors and gain a sustainable competitive position in the market. What was driving
output increases and enhanced production efficiency? What were the impediments to this process
Radiation damages and self-sputtering of high-radioactive dielectrics: spontaneous emission of submicronic dust particles
The spontaneous emission of submicronic particles from a surface of highradioactive
dielectrics has been under the experimental study for the first
time. Formation of disordered regions due to intrinsic irradiation and electron
sputtering of surface clusters processes turned out to be responsible
for the phenomenon under observation.Вперше експериментальним шляхом досліджено явище спонтанного вильоту субмікронних часток речовини з поверхні високорадіоактивних діелектриків. За явище, що спостерігається, відповідальні процеси формування розупорядкованих областей за рахунок внутрішнього самоопромінення та електронне розпилення поверхневих кластерів
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