19 research outputs found
Vacancy-Impurity Nanoclusters in Solid Solutions
The existence of vacancy--impurity clusters due to quantum properties of
vacancies in phase separated solid solutions of 4He in 3He is analyzed and
discussed. Additional mechanism called vacancy assisted nucleation is proposed.
According to this assumption the vacancy-impurity clusters should have b.c.c.
structure.Comment: 5 pages, 1 figure, Late
Stability of narrow beams in bulk Kerr-type nonlinear media
We consider (2+1)-dimensional beams, whose transverse size may be comparable
to or smaller than the carrier wavelength, on the basis of an extended version
of the nonlinear Schr\"{o}dinger equation derived from the Maxwell`s equations.
As this equation is very cumbersome, we also study, in parallel to it, its
simplified version which keeps the most essential term: the term which accounts
for the {\it nonlinear diffraction}. The full equation additionally includes
terms generated by a deviation from the paraxial approximation and by a
longitudinal electric-field component in the beam. Solitary-wave stationary
solutions to both the full and simplified equations are found, treating the
terms which modify the nonlinear Schr\"{o}dinger equation as perturbations.
Within the framework of the perturbative approach, a conserved power of the
beam is obtained in an explicit form. It is found that the nonlinear
diffraction affects stationary beams much stronger than nonparaxiality and
longitudinal field. Stability of the beams is directly tested by simulating the
simplified equation, with initial configurations taken as predicted by the
perturbation theory. The numerically generated solitary beams are always stable
and never start to collapse, although they display periodic internal
vibrations, whose amplitude decreases with the increase of the beam power.Comment: 7 pages, 6 figures Accepted for publication in PR
Lattice effects in the quasiparticle dynamics and kinetics
In this work we present a full selfconsistent set of
nonlinear equations which unifies the nonlinear elasticity
theory equations, the Boltzmannn transport theory and the
Maxwell equations for quasiparticles with arbitrary
dispersion laws in nonstationarily deformed crystals
with arbitrary (but linear) constitutive relations.
Transformations to replace the Galilean ones are obtained,
the quasiparticle mechanics in a Hamiltonian form is
deduced, and a Boltzmann-type transport equation (valid in
the whole Brillouin zone) is derived. The theory may be
applied to metals, semiconductors, quantum crystals,
low-dimensional structures etc
Vacancy distribution in a rotating solid
Vacancy distribution is considered in a rotating solid 4He immersed in a superfluid helium-II. Vacancies are considered as a quasiparticle gas of vacancions with a gap dispersion law. It is shown that the radial distribution depends on Poisson's ratio and practically not on Young's modulus. The treatment is based on a nonlinear theory unifying the elasticity theory equations and a Boltzmann-type transport equation valid for arbitrary angular velocities. The situation simulates, in a sense, the Kim and Chan rotational experiments where nonclassical inertia was observed. The model cannot be applied to solid 3He. We do not presuppose in this work any supersolid fraction