Search results for "classical"
showing 10 items of 2294 documents
Bending of ferrofluid droplet in rotating magnetic field
1999
Abstract This paper presents results concerning 2D ferrofluid droplet motion at high values of magnetic field and frequencies above a critical one with respect to droplet ability to follow field rotation. The boundary element method is used to solve 2D equations of a magnetic field and Stokes flow problems. If the viscosity of the ferrofluid is larger than that of the surrounding fluid, droplet exhibits bending, forming “S-shape”. Fluid flow inside the droplet is analyzed and the main stages of periodical rotation of a droplet are reported.
Diffusion in active magnetic colloids
2013
Abstract Properties of active colloids of circle swimmers are reviewed. As a particular example of active magnetic colloids the magnetotactic bacteria under the action of a rotating magnetic field is considered. The relation for a diffusion coefficient due to the random switching of the direction of rotation of their rotary motors is derived on the basis of the master equation. The obtained relation is confirmed by the direct numerical simulation of random trajectory of a magnetotactic bacterium under the action of the Poisson type internal noise due to the random switching of rotary motors. The results obtained are in qualitative and quantitative agreement with the available experimental r…
Probing Models of Extended Gravity using Gravity Probe B and LARES experiments
2014
We consider models of Extended Gravity and in particular, generic models containing scalar-tensor and higher-order curvature terms, as well as a model derived from noncommutative spectral geometry. Studying, in the weak-field approximation, the geodesic and Lense-Thirring processions, we impose constraints on the free parameters of such models by using the recent experimental results of the Gravity Probe B and LARES satellites.
Impact Energy Flux on Earth in the Last 150 Ma as Inferred from the Cratering Records
1998
We have used a compilation of 30 well-dated large impact craters on Earth (i.e., diameters larger than 5 km) younger than 150 Ma, their diameters, geochronologic ages, and the corresponding uncertainties to construct a graph summarizing our current knowledge on the influx of the impact energy onto the Earth as a function of time. From the crater diameters, we estimated the corresponding impact energies through suitable scaling laws. Then to each crater we associated a gaussian (bell) function of time centered at its age. Finally, all the bell functions corresponding to different craters were summed up and the resulting curve was plotted. From this curve, it is apparent that the 65 Ma old Ch…
The threshold behaviour of partial wave scattering amplitudes and theN/D-method
1964
It is shown that in partial wave dispersion relations the weight function on the unphysical cut must have a certain number of zeros in order to permit the correct threshold behaviour of the amplitude. Assuming a solution — not necessarily with correct threshold behaviour — of the once-subtractedN/D-equations to exist, the role of the subtraction parameters in repeatedly subtractedN/D equations is studied with particular reference to the threshold behaviour.
Waves Propagation in Turbulent Superfluid Helium in Presence of Combined Rotation and Counterflow
2010
A complete study of the propagation of waves (namely longitudinal density and temperature waves, longitudinal and transversal velocity waves and heat waves) in turbulent superfluid helium is made in three situations: a rotating frame, a thermal counterflow, and the simultaneous combination of thermal counterflow and rotation. Our analysis aims to obtain as much as possible information on the tangle of quantized vortices from the wave speed and attenuation factor of these different waves, depending on their relative direction of propagation with respect to the rotation vector.
Billiards in magnetic fields: A molecular dynamics approach
2009
We present a computational scheme based on classical molecular dynamics to study chaotic billiards in static external magnetic fields. The method allows to treat arbitrary geometries and several interacting particles. We test the scheme for rectangular single-particle billiards in magnetic fields and find a sequence of regularity islands at integer aspect ratios. In the case of two Coulomb-interacting particles the dynamics is dominated by chaotic behavior. However, signatures of quasiperiodicity can be identified at weak interactions, as well as regular trajectories at strong magnetic fields. Our scheme provides a promising tool to monitor the classical limit of many-electron semiconductor…
A missing link: What is behind de Broglie's "Periodic phenomenon"?
1996
The present work constitutes an attempt to give the interpretation of de Broglie's internal periodic phenomenon which ascribes the frequencym0c2/h to each single entity in its eigensystem of coordinates. This phenomenon provides existence in principle of the ideal proper-time scale, making it possible to identify the geometric proper-time interval with a physically existing one, thus ensuring the realization of basic postulates of the relativity theory. According to the latter, neither time nor de Broglie's frequency are invariant with respect to the Lorentz transformation of the coordinate system. A search for the fundamental invariant demands passing over to dimensionless quantities, and …
Quantum capacitance: a microscopic derivation
2010
We start from microscopic approach to many body physics and show the analytical steps and approximations required to arrive at the concept of quantum capacitance. These approximations are valid only in the semi-classical limit and the quantum capacitance in that case is determined by Lindhard function. The effective capacitance is the geometrical capacitance and the quantum capacitance in series, and this too is established starting from a microscopic theory.
Use of three detuned lasers to generate isolated attosecond pulses
2010
The dynamics of a one-dimensional atom driven by three-laser fields is investigated. The total electric field is made up of a fundamental laser field of intensity W cm−2 and wavelength λ = 820 nm and two weak lasers with larger wavelengths. The intensity of the two weak fields is with k = 0.25. The frequencies of the weak fields are and , with and . The three lasers have a Gaussian envelope of 72 fs FWHM. It is shown, by numerical computation and using the semiclassical theory of high-harmonic generation, that the atom interacting with this combined field is able to emit an isolated attosecond burst of radiation.