663 research outputs found

### Generalized Gravi-Electromagnetism

A self consistant and manifestly covariant theory for the dynamics of four
charges (masses) (namely electric, magnetic, gravitational, Heavisidian) has
been developed in simple, compact and consistent manner. Starting with an
invariant Lagrangian density and its quaternionic representation, we have
obtained the consistent field equation for the dynamics of four charges. It has
been shown that the present reformulation reproduces the dynamics of individual
charges (masses) in the absence of other charge (masses) as well as the
generalized theory of dyons (gravito - dyons) in the absence gravito - dyons
(dyons). key words: dyons, gravito - dyons, quaternion PACS NO: 14.80H

### Kirchhoff's Loop Law and the maximum entropy production principle

In contrast to the standard derivation of Kirchhoff's loop law, which invokes
electric potential, we show, for the linear planar electric network in a
stationary state at the fixed temperature,that loop law can be derived from the
maximum entropy production principle. This means that the currents in network
branches are distributed in such a way as to achieve the state of maximum
entropy production.Comment: revtex4, 5 pages, 2 figure

### Self-Similarity in Random Collision Processes

Kinetics of collision processes with linear mixing rules are investigated
analytically. The velocity distribution becomes self-similar in the long time
limit and the similarity functions have algebraic or stretched exponential
tails. The characteristic exponents are roots of transcendental equations and
vary continuously with the mixing parameters. In the presence of conservation
laws, the velocity distributions become universal.Comment: 4 pages, 4 figure

### Modelling the electric field applied to a tokamak

The vector potential for the Ohmic heating coil system of a tokamak is
obtained in semi-analytical form. Comparison is made to the potential of a
simple, finite solenoid. In the quasi-static limit, the time rate of change of
the potential determines the induced electromotive force through the
Maxwell-Lodge effect. Discussion of the gauge constraint is included.Comment: 13 pages, 7 figures, final versio

### Electron energy loss and induced photon emission in photonic crystals

The interaction of a fast electron with a photonic crystal is investigated by
solving the Maxwell equations exactly for the external field provided by the
electron in the presence of the crystal. The energy loss is obtained from the
retarding force exerted on the electron by the induced electric field. The
features of the energy loss spectra are shown to be related to the photonic
band structure of the crystal. Two different regimes are discussed: for small
lattice constants $a$ relative to the wavelength of the associated electron
excitations $\lambda$, an effective medium theory can be used to describe the
material; however, for $a\sim\lambda$ the photonic band structure plays an
important role. Special attention is paid to the frequency gap regions in the
latter case.Comment: 12 pages, 7 figure

### Information erasure and the generalized second law of black hole thermodynamics

We consider the generalized second law of black hole thermodynamics in the light of quantum information theory, in particular information erasure and Landauer’s principle (namely, that erasure of information produces at least the equivalent amount of entropy). A small quantum system outside a black hole in the Hartle-Hawking state is studied, and the quantum system comes into thermal equilibrium with the radiation surrounding the black hole. For this scenario, we present a simple proof of the generalized second law based on quantum relative entropy. We then analyze the corresponding information erasure process, and confirm our proof of the generalized second law by applying Landauer’s principle

### Dynamics and Thermodynamics of Systems with Long Range Interactions: an Introduction

We review theoretical results obtained recently in the framework of
statistical mechanics to study systems with long range forces. This fundamental
and methodological study leads us to consider the different domains of
applications in a trans-disciplinary perspective (astrophysics, nuclear
physics, plasmas physics, metallic clusters, hydrodynamics,...) with a special
emphasis on Bose-Einstein condensates.Comment: Chapter of the forthcoming "Lecture Notes in Physics" volume:
``Dynamics and Thermodynamics of Systems with Long Range Interactions'', T.
Dauxois, S. Ruffo, E. Arimondo, M. Wilkens Eds., Lecture Notes in Physics
Vol. 602, Springer (2002). (see http://link.springer.de/series/lnpp/

### Dynamical approach to the microcanonical ensemble

An analytical method to compute thermodynamic properties of a given
Hamiltonian system is proposed. This method combines ideas of both dynamical
systems and ensemble approaches to thermodynamics, providing de facto a
possible alternative to traditional Ensemble methods. Thermodynamic properties
are extracted from effective motion equations. These equations are obtained by
introducing a general variational principle applied to an action averaged over
a statistical ensemble of paths defined on the constant energy surface. The
method is applied first to the one dimensional (\beta)-FPU chain and to the two
dimensional lattice (\phi ^{4}) model. In both cases the method gives a good
insight of some of their statistical and dynamical properties.Comment: 5 pages, 4 figures, RevTe

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