1,919 research outputs found
Hamiltonian formalism for Fermi excitations in a plasma with a non-Abelian interaction
The Hamiltonian theory for the collective longitudinally polarized colorless
gluon excitations (plasmons) and for collective quark-antiquark excitations
with abnormal relation between chirality and helicity (plasminos) in a
high-temperature quark-gluon plasma (QGP) is developed. For this purpose,
Zakharov's formalism for constructing the wave theory in nonlinear media with
dispersion is used. A generalization of the Poisson superbracket involving both
commuting and anticommuting variables to the case of a continuous medium is
performed and the corresponding Hamilton equations are presented. The canonical
transformations including simultaneously both bosonic and fermionic degrees of
freedom of the collective excitations in QGP are discussed and a complete
system of the canonicity conditions for these transformations is written out.
An explicit form of the effective fourth-order Hamiltonians describing the
elastic scattering of plasmino off plasmino and plasmino off plasmon is found
and the Boltzmann type kinetic equations describing the processes of elastic
scattering are obtained. A detailed comparison of the effective amplitudes
defined within the (pseudo)classical Hamiltonian theory, with the corresponding
matrix elements calculated early in the framework of high-temperature quantum
chromodynamics in the so-called hard thermal loop approximation is performed.
This enables one to obtain, in particular, an explicit form of the vertex and
coefficient functions in the effective amplitudes and in the canonical
transformations, correspondingly, and also to define the validity of a purely
pseudoclassical approach in the Hamiltonian description of the dynamics of a
quark-gluon plasma. The problem of determining the higher-order coefficient
functions in the canonical transformations of fermionic and bosonic normal
variables is considered.Comment: 69 pages, 2 figures, typos corrected and references adde
Hamiltonian formalism for Bose excitations in a plasma with a non-Abelian interaction I: plasmon -- hard particle scattering
The Hamiltonian theory for the collective longitudinally polarized gluon
excitations (plasmons) coupling with classical high-energy test color-charged
particle propagating through a high-temperature gluon plasma is developed. A
generalization of the Lie-Poisson bracket to the case of a continuous medium
involving bosonic normal field variable
and a non-Abelian color
charge is performed and the corresponding Hamilton
equations are presented. The canonical transformations including simultaneously
both bosonic degrees of freedom of the soft collective excitations and degree
of freedom of hard test particle connecting with its color charge in the hot
gluon plasma are written out. A complete system of the canonicity conditions
for these transformations is derived. The notion of the plasmon number density
, which is
a nontrivial matrix in the color space, is introduced. An explicit form of the
effective fourth-order Hamiltonian describing elastic scattering of plasmon off
a hard color particle is found and the self-consistent system of Boltzmann type
kinetic equations taking into account the time evolution of the mean value of
the color charge of the hard particle is obtained. On the basis of these
equations, a model problem of interaction of two infinitly narrow wave packets
is considered. A system of nonlinear first-order ordinary differential
equations defining the dynamics of the interaction of the colorless and color components of the plasmon number density is
derived. The problem of determining the third- and fourth-order coefficient
functions entering into the canonical transformations of the original bosonic
variable and color charge
is discussed.Comment: 57 pages, 5 figure
Ryanodine Receptors Coupling Causes a Calcium Leak in Cardiac Cell
Here we introduce results of a mathematical modeling of calcium sparks in cardiac cells. We developed a model of the calcium release unit which includes a single sarcoplasmic reticulum (SR) lumen, a regular 9×9 cluster of RyRs and a dyadic space. 2D diffusion problem of Ca2+ ions across the dyadic space was solved thereby we reproduced Calcium-fnduced-Calcium-Release (CICR) effect and domino-like RyRs activation in the cluster. We take into account allosteric and Ca2+-induced coupling between RyRs. We show, that coupling between RyRs leads to the stability of Ca2+ sparks in amplitude and frequency. However, a sudden stop of spontaneous Ca2+ releases can be a result of strong allosteric coupling between RyRs. © 2018 Creative Commons Attribution.Russian Foundation for Basic Research, RFBR: 16-34-60223The project is supported by RFBR grant 16-34-60223. The work was carried out within the framework of the IIF UrB RAS theme No AAAA-A18-118020590031-8 and RF Government Act 211 of March 16, 2013 (agreement 02.A03.21.0006)
Spectroscopic and physical parameters of Galactic O-type stars. II. Observational constraints on projected rotational and extra broadening velocities as a function of fundamental parameters and stellar evolution
Rotation is of key importance for the evolution of hot massive stars,
however, the rotational velocities of these stars are difficult to determine.
Based on our own data for 31 Galactic O stars and incorporating similar data
for 86 OB supergiants from the literature, we aim at investigating the
properties of rotational and extra line-broadening as a function of stellar
parameters and at testing model predictions about the evolution of stellar
rotation. Fundamental stellar parameters were determined by means of the code
FASTWIND. Projected rotational and extra broadening velocities originate from a
combined Ft + GOF method. Model calculations published previously were used to
estimate the initial evolutionary masses. The sample O stars with Minit > 50
Msun rotate with less that 26% of their break-up velocity, and they also lack
objects with v sin i 35 Msun on the
hotter side of the bi-stability jump, the observed and predicted rotational
rates agree quite well; for those on the cooler side of the jump, the measured
velocities are systematically higher than the predicted ones. In general, the
derived extra broadening velocities decrease toward cooler Teff, whilst for
later evolutionary phases they appear, at the same v sin i, higher for
high-mass stars than for low-mass ones. None of the sample stars shows extra
broadening velocities higher than 110 km/s. For the majority of the more
massive stars, extra broadening either dominates or is in strong competition
with rotation. Conclusions: For OB stars of solar metallicity, extra broadening
is important and has to be accounted for in the analysis. When appearing at or
close to the zero-age main sequence, most of the single and more massive stars
rotate slower than previously thought. Model predictions for the evolution of
rotation in hot massive stars may need to be updated.Comment: 15 pages, 10 figures, accepted for publication in A &
Second-layer nucleation in coherent Stranski-Krastanov growth of quantum dots
We have studied the monolayer-bilayer transformation in the case of the
coherent Stranski-Krastanov growth. We have found that the energy of formation
of a second layer nucleus is largest at the center of the first-layer island
and smallest on its corners. Thus nucleation is expected to take place at the
corners (or the edges) rather than at the center of the islands as in the case
of homoepitaxy. The critical nuclei have one atom in addition to a compact
shape, which is either a square of i*i or a rectangle of i*(i-1) atoms, with
i>1 an integer. When the edge of the initial monolayer island is much larger
than the critical nucleus size, the latter is always a rectangle plus an
additional atom, adsorbed at the longer edge, which gives rise to a new atomic
row in order to transform the rectangle into the equilibrium square shape.Comment: 6 pages, 4 figures. Accepted version, minor change
Hamiltonian formalism for Bose excitations in a plasma with a non-Abelian interaction
We have developed the Hamiltonian theory for collective longitudinally
polarized colorless excitations (plasmons) in a high-temperature gluon plasma
using the general formalism for constructing the wave theory in nonlinear media
with dispersion, which was developed by V.E. Zakharov. In this approach, we
have explicitly obtained a special canonical transformation that makes it
possible to simplify the Hamiltonian of interaction of soft gluon excitations
and, hence, to derive a new effective Hamiltonian. The approach developed here
is used for constructing a Boltzmann-type kinetic equation describing elastic
scattering of collective longitudinally polarized excitations in a gluon plasma
as well as the effect of the so-called nonlinear Landau damping. We have
performed detailed comparison of the effective amplitude of the plasmon-plasmon
interaction, which is determined using the classical Hamilton theory, with the
corresponding matrix element calculated in the framework of high-temperature
quantum chromodynamics; this has enabled us to determine applicability limits
for the purely classical approach described in this study.Comment: 21 pages, 2 figure
Dynamical Quantum Phase Transition Without An Order Parameter
Short-time dynamics of many-body systems may exhibit non-analytical behavior
of the systems' properties at particular times, thus dubbed dynamical quantum
phase transition. Simulations showed that in the presence of disorder new
critical times appear in the quench evolution of the Ising model. We study the
physics behind these new critical times. We discuss the spectral features of
the Ising model responsible for the disorder-induced phase transitions. We
found the critical value of the disorder sufficient to induce the dynamical
phase transition as a function of the number of spins. Most importantly, we
argue that this dynamical phase transition while non-topological lacks a local
order parameter.Comment: 15 pages, 6 figure
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