123 research outputs found
Identification of Quasi-Stationary Dynamic Objects with the Use of Derivative Disproportion Functions
This paper presents an algorithm for designing a cryptographic system, in which the derivative
disproportion functions (key functions) are used. This cryptographic system is used for an operative
identification of a differential equation describing the movement of quasi-stationary objects. The symbols to be transmitted are encrypted by the sum of at least two of these functions combined with random coefficients. A new algorithm is proposed for decoding the received messages making use of important properties of the derivative disproportion functions
Statistical Properties of Charmonium Spectrum and a New Mechanism of J/\psi Suppression
The statistical properties of Charmonium energy spectrum determined by the
Bethe-Salpeter equation are investigated. It is found that the regular motion
of the system can be expected at a small value of color screening
mass but the chaotic motion at a large one. It is shown that the level mixing
due to color screening serves as a new mechanism resulting in the J/
suppression. Moreover, this kind of suppression can occur before the color
screening mass reaches its critical value for J/ dissociation. It implies
that a strong J/ suppression is possible in the absence of dissociation
of J/.Comment: 13 latex pages, 2 figures. Phys. Rev. C in pres
Intrinsic Spin Lifetime of Conduction Electrons in Germanium
We investigate the intrinsic spin relaxation of conduction electrons in
germanium due to electron-phonon scattering. We derive intravalley and
intervalley spin-flip matrix elements for a general spin orientation and
quantify the resulting anisotropy in spin relaxation. The form of the
intravalley spin-flip matrix element is derived from the eigenstates of a
compact spin-dependent Hamiltonian in the
vicinity of the point (where thermal electrons are populated in Ge). Spin
lifetimes from analytical integrations of the intravalley and intervalley
matrix elements show excellent agreement with independent results from
elaborate numerical methods.Comment: 13 pages, 2 figure
The problem of nonlinear Landau damping in quark-gluon plasma
On the basis of the semiclassical equations for quark-gluon plasma (QGP) and
Yang-Mills equation, the generalized kinetic equation for waves with regard to
its interaction is obtained. The physical mechanisms defining nonlinear
scattering of a plasmon by QGP particles are analysed. The problem on a
connection of nonlinear Landau damping rate of longitudinal oscillation with
damping rate, obtained on the basis of hard thermal loops approximation, is
considered.Comment: 33 page
On the self-consistent spin-wave theory of layered Heisenberg magnets
The versions of the self-consistent spin-wave theories (SSWT) of
two-dimensional (2D) Heisenberg ferro- and antiferromagnets with a weak
interlayer coupling and/or magnetic anisotropy, that are based on the
non-linear Dyson-Maleev, Schwinger, and combined boson-pseudofermion
representations, are analyzed. Analytical results for the temperature
dependences of (sublattice) magnetization and short-range order parameter, and
the critical points are obtained. The influence of external magnetic field is
considered. Fluctuation corrections to SSWT are calculated within a
random-phase approximation which takes into account correctly leading and
next-leading logarithmic singularities. These corrections are demonstrated to
improve radically the agreement with experimental data on layered perovskites
and other systems. Thus an account of these fluctuations provides a
quantitative theory of layered magnets.Comment: 46 pages, RevTeX, 7 figure
QCD in the nuclear medium and effects due to Cherenkov gluons
The equations of in-medium gluodynamics are proposed. Their classical lowest
order solution is explicitly shown for a color charge moving with constant
speed. For nuclear permittivity larger than 1 it describes emission of
Cherenkov gluons resembling results of classical electrodynamics. The values of
the real and imaginary parts of the nuclear permittivity are obtained from the
fits to experimental data on the double-humped structure around the away-side
jet obtained at RHIC. The dispersion of the nuclear permittivity is predicted
by comparing the RHIC, SPS and cosmic ray data. This is important for LHC
experiments. Cherenkov gluons may be responsible for the asymmetry of dilepton
mass spectra near rho-meson, observed in the SPS experiment with excess in the
low-mass wing of the resonance. This feature is predicted to be common for all
resonances. The "color rainbow" quantum effect might appear according to higher
order terms of in-medium QCD if the nuclear permittivity depends on color.Comment: 29 p., 4 figs; for "Phys. Atom. Nucl." volume dedicated to 80th
birthday of L.B. Okun; minor corrections on pp. 11 and 13 in v
Consensus position of endocrinologists and pathologists on coding causes of death in patients with diabetes mellitus (expert opinion)
Coding of the causes of death of patients with diabetes mellitus (DM) in the Russian Federation is one of the long-discussed problems, due to the comorbidity of diabetes and cardiovascular diseases (CVD) and a number of contradictions in the key regulatory documents regulating the statistics of mortality in this category of patients, which acquires particular relevance in the context of the coronavirus pandemic, due to its negative impact on the outcomes of the course of COVID-19 and mortality risks. In pursuance of the decisions of the Minutes of the meeting of the working group under the project committee of the National Project «Health» on identifying patterns in the formation of mortality rates of the population dated January 20, 2021 No. 1, chaired by Deputy Prime Minister of the Russian Federation T.A. Golikova, experts of two directions - endocrinology and pathological anatomy, prepared a Draft of agreed recommendations on the Rules for coding the causes of death of patients with diabetes, causing the greatest problems in terms of the use of ICD-10 when choosing the initial cause of death, including in the case of death from CVD and COVID-19
The Hubbard model within the equations of motion approach
The Hubbard model has a special role in Condensed Matter Theory as it is
considered as the simplest Hamiltonian model one can write in order to describe
anomalous physical properties of some class of real materials. Unfortunately,
this model is not exactly solved except for some limits and therefore one
should resort to analytical methods, like the Equations of Motion Approach, or
to numerical techniques in order to attain a description of its relevant
features in the whole range of physical parameters (interaction, filling and
temperature). In this manuscript, the Composite Operator Method, which exploits
the above mentioned analytical technique, is presented and systematically
applied in order to get information about the behavior of all relevant
properties of the model (local, thermodynamic, single- and two- particle ones)
in comparison with many other analytical techniques, the above cited known
limits and numerical simulations. Within this approach, the Hubbard model is
shown to be also capable to describe some anomalous behaviors of the cuprate
superconductors.Comment: 232 pages, more than 300 figures, more than 500 reference
Real-time Relaxation and Kinetics in Hot Scalar QED: Landau Damping
The real time evolution of field condensates with soft length scales
k^{-1}>(eT)^{-1} is solved in hot scalar electrodynamics, with a view towards
understanding relaxational phenomena in the QGP and the electroweak plasma. We
find that transverse gauge invariant non-equilibrium expectation values of
fields relax via {\em power laws} to asymptotic amplitudes that are determined
by the quasiparticle poles. The long time relaxational dynamics and relevant
time scales are determined by the behaviour of the retarded self-energy not at
the small frequencies, but at the Landau damping thresholds. This explains the
presence of power laws and not of exponential decay. Furthermore, we derive the
influence functional, the Langevin equation and the fluctuation-dissipation
theorem for the soft modes, identifying the correlation functions that emerge
in the classical limit. We show that a Markovian approximation fails to
describe the dynamics {\em both} at short and long times. We also introduce a
novel kinetic approach that goes beyond the standard Boltzmann equation and
incorporates off-shell processes and find that the distribution function for
soft quasiparticles relaxes with a power law through Landau damping. We also
find an unusual dressing dynamics of bare particles and anomalous (logarithmic)
relaxation of hard quasiparticles.Comment: 41 pages, 5 figures, uses revtex, replaced with version to appear in
Phys. Rev.
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