Non-equilibrium melting processes of silicate melts with different silica content at low-temperature plasma

This article is devoted to research the possibility of high-temperature silicate melts producing from different silica content at low-temperature plasma taking into account non-equilibrium melting processes

Frictional drag between quantum wells mediated by fluctuating electromagnetic field

We use the theory of the fluctuating electromagnetic field to calculate the frictional drag between nearby two-and three dimensional electron systems. The frictional drag results from coupling via a fluctuating electromagnetic field, and can be considered as the dissipative part of the van der Waals interaction. In comparison with other similar calculations for semiconductor two-dimensional system we include retardation effects. We consider the dependence of the frictional drag force on the temperature $T$, electron density and separation $d$. We find, that retardation effects become dominating factor for high electron densities, corresponding thing metallic film, and suggest a new experiment to test the theory. The relation between friction and heat transfer is also briefly commented on.Comment: 14 pages, 4 figure

Non-equilibrium melting processes of silicate melts with different silica content at low-temperature plasma

This article is devoted to research the possibility of high-temperature silicate melts producing from different silica content at low-temperature plasma taking into account non-equilibrium melting processes

PROBABILISTIC MODEL OF BEAM–PLASMA INTERACTION IN RANDOMLY INHOMOGENEOUS PLASMA

International audienceWe propose a new model that describes beam–plasma interaction in the presence of random density fluctuationswith a known probability distribution. We use the property that, for the given frequency, the probabilitydistribution of the density fluctuations uniquely determines the probability distribution of the phase velocity ofwaves. We present the system as discrete and consisting of small, equal spatial intervals with a linear densityprofile. This approach allows one to estimate variations in wave energy density and particle velocity, depending onthe density gradient on any small spatial interval. Because the characteristic time for the evolution of the electrondistribution function and the wave energy is much longer than the time required for a single wave–particle resonantinteraction over a small interval, we determine the description for the relaxation process in terms of averagedquantities. We derive a system of equations, similar to the quasi-linear approximation, with the conventionalvelocity diffusion coefficient D and the wave growth rate γ replaced by the average in phase space, by making useof the probability distribution for phase velocities and by assuming that the interaction in each interval isindependent of previous interactions. Functions D and γ are completely determined by the distribution function forthe amplitudes of the fluctuations. For the Gaussian distribution of the density fluctuations, we show that therelaxation process is determined by the ratio of beam velocity to plasma thermal velocity, the dispersion of thefluctuations, and the width of the beam in the velocity space

Computation of the asymptotic states of modulated open quantum systems with a numerically exact realization of the quantum trajectory method

Quantum systems out of equilibrium are presently a subject of active research, both in theoretical and experimental domains. In this work we consider time-periodically modulated quantum systems which are in contact with a stationary environment. Within the framework of a quantum master equation, the asymptotic states of such systems are described by time-periodic density operators. Resolution of these operators constitutes a non-trivial computational task. To go beyond the current size limits, we use the quantum trajectory method which unravels master equation for the density operator into a set of stochastic processes for wave functions. The asymptotic density matrix is calculated by performing a statistical sampling over the ensemble of quantum trajectories, preceded by a long transient propagation. We follow the ideology of event-driven programming and construct a new algorithmic realization of the method. The algorithm is computationally efficient, allowing for long 'leaps' forward in time, and is numerically exact in the sense that, being given the list of uniformly distributed (on the unit interval) random numbers, $\{\eta_1, \eta_2,...,\eta_n\}$, one could propagate a quantum trajectory (with $\eta_i$'s as norm thresholds) in a numerically exact way. %Since the quantum trajectory method falls into the class of standard sampling problems, performance of the algorithm %can be substantially improved by implementing it on a computer cluster. By using a scalable $N$-particle quantum model, we demonstrate that the algorithm allows us to resolve the asymptotic density operator of the model system with $N = 2000$ states on a regular-size computer cluster, thus reaching the scale on which numerical studies of modulated Hamiltonian systems are currently performed

Dissipative Van der Waals interaction between a small particle and a metal surface

We use a general theory of the fluctuating electromagnetic field to calculate the friction force acting on a small neutral particle, e.g., a physisorbed molecule, or a nanoscale object with arbitrary dispersive and absorptive dielectric properties, moving near a metal surface. We consider the dependence of the electromagnetic friction on the temperature $T$, the separation $d$, and discuss the role of screening, non-local and retardation effects. We find that for high resistivity materials, the dissipative van der Waals interaction can be an important mechanism of vibrational energy relaxation of physisorbed molecules, and friction for microscopic solids. Several controversial topics related to electromagnetic dissipative shear stress is considered. The problem of local heating of the surface by an STM tip is also briefly commented on.Comment: 11 pages, No figure

Quantum field theory of the van der Waals friction

The van der Waals friction between two semi-infinite solids, and between a small neutral particle and semi-infinite solid is reconsidered on the basis of thermal quantum field theory in the Matsubara formulation. The calculation of the friction to linear order in the sliding velocity is reduced to the finding of the equilibrium Green functions. Thus this approach cab be extended for bodsies with complex geometry. The friction calculated in this approach agrees with the friction calculated using a dynamical modification of the Lifshitz theory, which is based on the fluctuation-dissipation therem. We show that the van der Waals fricxtion can be measured in non-contact friction experiment using state-of-the art equipment

Radiative heat transfer between nanostructures

We simplify the formalism of Polder and Van Hove [Phys.Rev.B {\bf 4}, 3303(1971)], which was developed to calculate the heat transfer between macroscopic and nanoscale bodies of arbitrary shape, dispersive and adsorptive dielectric properties. In the non-retarded limit, at small distances between the bodies, the problem is reduced to the solution of an electrostatic problem. We apply the formalism to the study of the heat transfer between: (a) two parallel semi-infinite bodies, (b) a semi-infinite body and a spherical body, and (c) that two spherical bodies. We consider the dependence of the heat transfer on the temperature $T$, the shape and the separation $d$. We determine when retardation effects become important.Comment: 11 pages, 5 figure