994,419 research outputs found
Geometrical optics method in the theory of channeling of high energy particles in crystals
The process of scattering of fast charged particles in thin crystals is
considered in the transitional range of thicknesses, between those at which the
channeling phenomenon is not developed and those at which it is realized. The
possibility is shown of application of the methods of geometrical optics for
description of the scattering process. The dependence is studied of the total
scattering cross-section of ultrarelativistic positrons on target thickness in
this range of crystal thicknesses. In the case of ultrarelativistic particles
channeling the possibility is shown of the existence of an effect analogical to
the Ramsauer-Townsend effect of conversion into zero of the total scattering
cross-section at some values of crystal thickness. The important role is
outlined of the Morse-Maslov index that enters into the wave function
expression in the geometrical optics method.Comment: 6 pages, 2 figure
Dimensional transmutation and symmetry breaking in Maxwell- Chern-Simons scalar QED
The mechanism of dimensional transmutation is discussed in the context of
Maxwell-Chern-Simons scalar QED. The method used is non-perturbative. The
effective potential describes a broken symmetry state. It is found that the
symmetry breaking vacuum is more stable when the Chern-Simons mass is different
from zero.
Pacs number: 11.10.Ef, 11.10.Gh.Comment: e-mail: [email protected]
Chiral Magnetic Skyrmions with Arbitrary Topological Charge ("skyrmionic sacks")
We show that continuous and spin-lattice models of chiral ferro- and
antiferromagnets provide the existence of an infinite number of stable soliton
solutions of any integer topological charge. A detailed description of the
morphology of new skyrmions and the corresponding energy dependencies are
provided. The considered model is general, and is expected to predict a
plethora of particle-like states which may occur in various chiral magnets
including atomic layers, e.g., PdFe/Ir(111), rhombohedral GaVS
semiconductor, B20-type alloys as MnFeGe, MnFeSi,
FeCoSi, CuOSeO, acentric tetragonal Heusler compounds
Language as an Evolving Word Web
Human language can be described as a complex network of linked words. In such
a treatment, each distinct word in language is a vertex of this web, and
neighboring words in sentences are connected by edges. It was recently found
(Ferrer and Sol\'e) that the distribution of the numbers of connections of
words in such a network is of a peculiar form which includes two pronounced
power-law regions. Here we treat language as a self-organizing network of
interacting words. In the framework of this concept, we completely describe the
observed Word Web structure without fitting.Comment: 4 pages revtex, 2 figure
Time of avalanche mixing of granular materials in a half filled rotated drum
The avalanche mixing of granular solids in a slowly rotated 2D upright drum
is studied. We demonstrate that the account of the difference between
the angle of marginal stability and the angle of repose of the granular
material leads to a restricted value of the mixing time for a half
filled drum. The process of mixing is described by a linear discrete difference
equation. We show that the mixing looks like linear diffusion of fractions with
the diffusion coefficient vanishing when is an integer part of .
Introduction of fluctuations of supresses the singularities of
and smoothes the dependence .Comment: 4 pages revtex (twocolumn, psfig), 2 figure
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