61 research outputs found
Investigation of X-radiation of the moon by means of the lunar satellite ''Luna-10''
Lunik-10 observations of lunar X ray
Calculation of the Raman G peak intensity in monolayer graphene: role of Ward identities
The absolute integrated intensity of the single-phonon Raman peak at 1580
cm^{-1} is calculated for a clean graphene monolayer. The resulting intensity
is determined by the trigonal warping of the electronic bands and the
anisotropy of the electron-phonon coupling, and is proportional to the second
power of the excitation frequency. The main contribution to the process comes
from the intermediate electron-hole states with typical energies of the order
of the excitation frequency, contrary to what has been reported earlier. This
occurs because of strong cancellations between different terms of the
perturbation theory, analogous to Ward identities in quantum electrodynamics
Study of the soft corpuscular radiation on the AMS ''Luna-10''
Lunar-10 measurements of soft corpuscular radiatio
X-radiation of the moon and Roentgen cosmic background according to data of AMS ''Luna-12''
Satellite measurements of lunar soft X radiation, and Roentgen cosmic backgroun
Image and Spectrum of the Sun in the Region 9.5-200 Angstrom
Short wave ultraviolet image and spectrum of sun obtained during course of X-ray flar
Formation of the internal structure of solids under severe action
On the example of a particular problem, the theory of vacancies, a new form
of kinetic equations symmetrically incorporation the internal and free energies
has been derived. The dynamical nature of irreversible phenomena at formation
and motion of defects (dislocations) has been analyzed by a computer
experiment. The obtained particular results are extended into a thermodynamic
identity involving the law of conservation of energy at interaction with an
environment (the 1st law of thermodynamics) and the law of energy
transformation into internal degree of freedom (relaxation). The identity is
compared with the analogous Jarzynski identity. The approach is illustrated by
simulation of processes during severe plastic deformation, the Rybin kinetic
equation for this case has been derived.Comment: 9 pages, 5 figure
Transport coefficients of O(N) scalar field theories close to the critical point
We investigate the critical dynamics of O(N)-symmetric scalar field theories
to determine the critical exponents of transport coefficients as a second-order
phase transition is approached from the symmetric phase. A set of stochastic
equations of motion for the slow modes is formulated, and the long wavelength
dynamics is examined for an arbitrary number of field components, , in the
framework of the dynamical renormalization group within the
expansion. We find that for a single component scalar field theory, N=1, the
system reduces to the model C of critical dynamics, whereas for the model
G is effectively restored owing to dominance of O(N)-symmetric charge
fluctuations. In both cases, the shear viscosity remains finite in the critical
region. On the other hand, we find that the bulk viscosity diverges as the
correlation length squared, for N=1, while it remains finite for .Comment: revised for publication in PR
Theory of resonant multiphonon Raman scattering in graphene
We present a detailed calculation of intensities of two-phonon and
four-phonon Raman peaks in graphene. Writing the low-energy hamiltonian of the
interaction of electrons with the crystal vibrations and the electromagnetic
field from pure symmetry considerations, we describe the system in terms of
just a few independent coupling constants, considered to be parameters of the
theory. The electron scattering rate is introduced phenomenologically as
another parameter. The results of the calculation are used to extract
information about these parameters from the experimentally measured Raman peak
intensities.Comment: 49 pages, 25 figure
Negative Refraction in Perspective
The concept of negative refraction is attracting a lot of attention. The
initial ideas and the misconceptions that have arisen are discussed in
sufficient detail to understand the conceptual structure that binds negative
refraction to the existence of backward wave and forward wave phenomena. A
presentation of the properties of isotropic media supporting backward waves is
followed by a discussion of negative phase velocity media, causality,
anisotropic crystals and some connections to photonic crystals. The historical
background is always coupled to a detailed presentation of all the issues. The
paper is driven numerically and is illustrated with the outcomes of original
FDTD simulations
Control of planar nonlinear guided waves and spatial solitons with a left-handed medium
The evidence that double negative media, with an effective negative
permittivity, and an effective negative permeability, can be manufactured to
operate at frequencies ranging from microwave to optical is ushering in a new
era of metamaterials. They are referred to here as 'left-handed', even though a
variety of names is evident from the literature. In anticipation of a demand
for highly structured integrated practical waveguides, this paper addresses the
impact of this type of medium upon waveguides that can be also nonlinear. After
an interesting historical overview and an exposure of some straightforward
concepts, a planar guide is investigated, in which the waveguide is a slab
consisting of a left-handed medium sandwiched between a substrate and cladding
that are simple dielectrics. The substrate and cladding display a Kerr-type
nonlinear response. Because of the nonlinear properties of the Kerr media, the
power flow direction can be controlled by the intensity of the electric field.
A comprehensive finite-difference-time-domain (FDTD) analysis is presented that
concentrates upon spatial soliton behaviour. An interesting soliton-lens
arrangement is investigated that lends itself to a novel cancellation effect.Comment: 19 pages, 11 figure
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