Search results for "classical"
showing 10 items of 2294 documents
Exact analytic expressions for electromagnetic propagation in a finite one-dimensional periodic multilayer
2004
Translation Matrix Formalism has been used to find an exact analytic solution for light propagation in a finite one-dimensional (1-D) periodic stratified structure. This modal approach allows to derive a closed formula for the electric field in every point of the structure, by simply imposing a convenient form for the boundary conditions. As an example it is also shown how to extend this result to gratings featuring defects.
Monte Carlo Test of the Classical Theory for Heterogeneous Nucleation Barriers
2010
Flat walls facilitate the condensation of a supersaturated vapor: Classical theory of heterogeneous nucleation predicts that the free energy barrier $\Delta F_{\rm het}^*$ which needs to be overcome for the formation of sphere-cap shaped nucleation seeds is smaller than the barrier $\Delta F^*_{\rm hom}$ for spherical droplets in the bulk by a factor $0<f(\theta)<1$, which only depends on the contact angle $\theta$. In this letter we compute both $\Delta F^*_{\rm hom}$ and $\Delta F^*_{\rm het}$ from Monte Carlo simulations and test the theory for the lattice gas model (for which $\theta$ can be readily controlled). Even though the theory is only based on macroscopic arguments, it is shown …
Classical Field Theory of Gravitation
2012
The classical field theories developed in the preceding chapters all have in common that they are formulated on a flat spacetime, i.e. on a four-manifold which is a Euclidean space and which locally is decomposable into a direct product M 4 = ℝR3 ℝR of a physical space ℝR3 x of motions, and a time axis ℝRt. The first factor is the threedimensional space as it is perceived by an observer at rest while the time axis displays the (coordinate) time that he/she measures on his/her clocks. This spacetime is endowed with the Poincare group as the invariance group of physical laws and inherits the corresponding specific causality structure.
A wind tunnel study of the effects of collision processes on the shape and oscillation for moderate-size raindrops
2014
Abstract Drop–drop collision experiments were carried out at the Mainz vertical wind tunnel. Water drops of 2.5 mm diameter were freely floated at their terminal velocities in a vertical air stream and collided with 0.5 mm diameter droplets. The collisions were recorded with a high speed digital video camera at a frame rate of 1000 per second. Altogether 116 collision events were observed, 75 of which ended with coalescence, and the rest with filament type breakup. The coalescence efficiency and its dependence on the Weber number and on the eccentricity of the colliding drops showed good agreement with earlier numerical studies. Thirty-six recorded collisions were further analyzed in order …
Anti-phase wave patterns in a ring of electrically coupled oscillatory neurons
2013
International audience; Space-time dynamics of the network system modeling collective behavior of electrically coupled nonlinear cells is investigated. The dynamics of a local cell is described by the dimensionless Morris-Lecar system. It is shown that such a system yields a special class of traveling localized collective activity so called "anti-phase wave patterns". The mechanisms of formation of the patterns are discussed and the region of their existence is obtained by using the weakly coupled oscillators theory.
Collective forces in scalar active matter.
2020
Large-scale collective behavior in suspensions of many particles can be understood from the balance of statistical forces emerging beyond the direct microscopic particle interactions. Here we review some aspects of the collective forces that can arise in suspensions of self-propelled active Brownian particles: wall forces under confinement, interfacial forces, and forces on immersed bodies mediated by the suspension. Even for non-aligning active particles, these forces are intimately related to a non-uniform polarization of particle orientations induced by walls and bodies, or inhomogeneous density profiles. We conclude by pointing out future directions and promising areas for the applicati…
Intermittent-Type Chaos in Nonsinusoidal Driven Oscillators
2000
The intermittent-type chaos occurring in rf- and dc- nonsinusoidal driven oscillators is investigated analytically and numerically. The attention is focused on a general class of oscillators in which the total potential VRP(,r) is the Remoissenet-Peyrard potential which has constant amplitude and is 2π-periodic in , and whose shape can be varied as a function of parameter r ( |r| < 1). A simple physical model for calculating analytically the Melnikov function is proposed. The onset of chaos is studied through an analysis of the phase space, a construction of the bifurcation diagram and a computation of the Lyapunov exponent. The parameter regions of chaotic behaviour predicted by the theore…
Large-scale normal fluid circulation in helium superflows
2017
We perform fully-coupled numerical simulations of helium II pure superflows in a channel, with vortex- line density typical of experiments. Peculiar to our model is the computation of the back-reaction of the superfluid vortex motion on the normal fluid and the presence of solid boundaries. We recover the uniform vortex-line density experimentally measured employing second sound resonators and we show that pure superflow in helium II is associated with a large-scale circulation of the normal fluid which can be detected using existing particle-tracking visualization techniques.
Instabilities in a staircase stratified shear flow
2017
We study stratified shear flow instability where the density profile takes the form of a staircase of interfaces separating uniform layers. Internal gravity waves riding on density interfaces can r...
The nonadiabatic general-relativistic stellar oscillations
1990
We have derived the equations which govern the linear nonadiabatic general-relativistic radial oscillations. The perturbation produces a heat flux that is coupled with the geometry, through the Einstein field equations of a stellar configuration. The classical limit is recovered. The stability conditions are examined by means of a simplified one-zone model.