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At least 19 recordsLinked to original sources
arXiv2007

A POVM view of the ensemble approach to polarization optics

Statistical ensemble formalism of Kim, Mandel and Wolf (J. Opt. Soc. Am. A 4, 433 (1987)) offers a realistic model for characterizing the effect of stochastic non-image forming optical media on the state of polarization of transmittedlight. With suitable choice of the Jones ensemble, various Mueller transformations - some of which have been unknown so far - are deduced. It is observed that the ensemble approach is formally identical to the positive operator valued measures (POVM) on the quantum density matrix. This observation, in combination with the recent suggestion by Ahnert and Payne (Phys. Rev. A 71, 012330, (2005)) - in the context of generalized quantum measurement on single photon polarization states - that linear optics elements can be employed in setting up all possible POVMs, enables us to propose a way of realizing different types of Mueller devices.

physics.optics↗
arXiv2007

Relativeca Dopplera efekto ĉe unuforme akcelata movo -- II

Extending physics/0701092, a light source of monochromatic radiation, in rectilinear motion under constant proper acceleration, passes near an observer at rest. In the context of special relativity, we describe the observed Doppler effect. We describe also the interesting discontinuous effect when riding through occurs. An English version of this article is available. ----- Da^urigante physics/0701092, luma fonto de unukolora radiado ^ce rekta movo ^ce konstanta propra akcelo pasas preter restanta observanto. ^Ce la special-relativeco, ni priskribas la observatan Doppleran efikon. Ni anka^u priskribas la interesan nekontinuan efikon se trapaso okazas.

physics.gen-ph↗
arXiv2007

An English translation o Bertrand's theorem

A beautiful theorem due to J. L. F. Bertrand concerning the laws of attraction that admit bounded closed orbits for arbitrarily chosen initial conditions is translated from French into English.

physics.class-ph↗
arXiv2007

A new numerical algorithm for Low Mach number supercritical fluids

A new algorithm has been developed to compute low Mach Numbers supercritical fluid flows. The algorithm is applied using a finite volume method based on the SIMPLER algorithm. Its main advantages are to decrease significantly the CPU time, and the possibility for supercritical fluid flow modelisation to use other discretisation methods (such as spectral methods and/or finite differences) and other algorithms such as PISO or projection. It makes it possible to solve 3D problems within reasonable CPU time even when considering complex equations of state. The algorithm is given after first a brief description of the previously existing algorithm to solve for supercritical fluids. The side and bottom heated near critical carbon dioxide filled cavity problems are respectively solved and compared to the previously obtained results.

physics.class-ph↗
arXiv2007

The Volume Capture in Structures with Variable Curvature

The volume capture in classical relativistic mechanics is considered as a scattering process for the high energy charged particles in a field with no central or mirror symmetry. The parameters of volume capture for potentials with smooth variable curvature are received and analyzed.

physics.acc-ph↗
arXiv2007

Gravity-like potential traps light and stretches supercontinuum in photonic crystal fibers

The use of photonic crystal fibers pumped by femtosecond pulses has enabled the generation of broad optical supercontinua with nano-joule input energies. This striking discovery has applications ranging from spectroscopy and metrology to telecommunication and medicine. Amongst the physical principles underlying supercontinuum generation are soliton fission, a variety of four-wave mixing processes, Raman induced soliton self-frequency shift, and dispersive wave generation mediated by solitons. Although all of the above effects contribute to supercontinuum generation none of them can explain the generation of blue and violet light from infrared femtosecond pump pulses, which has been seen already in the first observations of the supercontinuum in photonic crystal fibers. In this work we argue that the most profound role in the shaping of the short-wavelength edge of the continuum is played by the effect of radiation trapping in a gravity-like potential created by accelerating solitons. The underlying physics of this effect has a straightforward analogy with the inertial forces acting on an observer moving with a constant acceleration.

physics.optics↗
arXiv2007

Quantum electrodynamics and experiment demonstrate the non-retarded nature of electrodynamical force fields

In quantum electrodynamics, the quantitatively most successful theory in the history of science, intercharge forces obeying the inverse square law are due to the exchange of space-like virtual photons. The fundamental quantum process underlying applications as diverse as the gyromagnetic ratio of the electron and electrical machinery is then Møller scattering $ee \to ee$. Analysis of the quantum amplitude for this process shows that the corresponding intercharge force acts instantaneously. This prediction has been verified in a recent experiment.

physics.class-ph↗
arXiv2007

The Equations of Motion of a Charged Particle in the Five-Dimensional Model of the General Relativity Theory with the Four-Dimensional Nonholonomic Velocity Space

We consider the four-dimensional nonholonomic distribution defined by the 4-potential of the electromagnetic field on the manifold. This distribution has a metric tensor with the Lorentzian signature $(+,-,-,-)$, therefore, the causal structure appears as in the general relativity theory. By means of the Pontryagin's maximum principle we proved that the equations of the horizontal geodesics for this distribution are the same as the equations of motion of a charged particle in the general relativity theory. This is a Kaluza -- Klein problem of classical and quantum physics solved by methods of sub-Lorentzian geometry. We study the geodesics sphere which appears in a constant magnetic field and its singular points. Sufficiently long geodesics are not optimal solutions of the variational problem and define the nonholonomic wavefront. This wavefront is limited by a convex elliptic cone. We also study variational principle approach to the problem. The Euler -- Lagrange equations are the same as those obtained by the Pontryagin's maximum principle if the restriction of the metric tensor on the distribution is the same.

math.DG↗
arXiv2007

On the Rayleigh theorem for inflectional velocity instability of inviscid flows

It is exactly proved that the classical Rayleigh Theorem on inflectional velocity instability is wrong which states that the necessary condition for instability of inviscid flow is the existence of an inflection point on the velocity profile. It is shown that the disturbance amplified in 2D inviscid flows is necessarily 3D. After the break down of T-S wave in 2D parallel flows, the disturbance becomes a type of spiral waves which proceed along the streamwise direction. This is just the origin of formation of streamwise vortices.

physics.flu-dyn↗
arXiv2007

A numerical study of heat island flows in an open domain: Stationary solutions

We present two dimensional numerical simulations of a natural convection problem in an unbounded domain. A thermal stratification is applied in the vertical direction and the flow circulation is induced by a heat island located on the ground. For this problem, thermal perturbations are convected in the horizontal direction far from the heated element so that very elongated computational domains have to be used in order to compute accurate numerical solutions. To avoid this difficulty thermal sponge layers are added at the vertical boundaries. With this approach, stationary solutions at $Ra\le 10^5$ are investigated. Boussinesq equations are discretized with a second-order finite volume scheme on a staggered grid combined with a second-order projection method for the time integration.

math.NA↗
arXiv2007

A planar vacuum diode with electrons possessing velocity distribution function

The current-voltage characteristic of a planar vacuum diode with electrons possessing velocity distribution function during an emission from the cathode (electron beam) is theoretically considered in this article. The electron beam movement in the volume is examined. An integral-differential equation for the electric field potential is got in a correct form. A current-voltage characteristic of the diode for a model function of the velocity distribution of the emitted electrons is obtained.

physics.gen-ph↗
arXiv2008

Schwinger's Magnetic Model of Matter: Can It Help Us With Grand Unification?

Many have argued that research on grand unification or local realistic physics will not be truly relevant until it makes predictions verified by experiment, different from the prediction of prior theory (the standard model). This paper proposes a new strategy (and candidate Lagrangians) for such models; that strategy in turn calls for reconsideration of Schwinger's magnetic model of matter. High priority should be given to experiments which fully confirm or deny recent scattering calculations which suggest the presence of van der Waals effects in low energy p-p and pi-pi scattering, consistent with Schwinger's model and inconsistent with QCD as we know it (with a mass gap). I briefly discuss other evidence, which does not yet rule out Schwinger's theory. A recent analysis of hadron masses also seems more consistent with the Schwinger model than with QCD.

physics.gen-ph↗
arXiv2007

Comments on ``Spin Connection Resonance in Gravitational General Relativity''

We comment on a recent article of M.W.Evans, Acta Physica Polonica B38 (2007) 2211. We point out that the equations underlying Evans' theory are highly problematic. Moreover, we demonstrate that the so-called ``spin connection resonance'', predicted by Evans, cannot be derived from the equation he used. We provide an exact solution of Evans' corresponding equation and show that is has definitely no resonance solutions.

physics.class-ph↗
arXiv2007

Structure of the Nondiffracting (Localized) Waves, and some interesting applications

Since the early works[1-4] on the so-called nondiffracting waves (called also Localized Waves), a great deal of results has been published on this important subject, from both the theoretical and the experimental point of view. Initially, the theory was developed taking into account only free space; however, in recent years, it has been extended for more complex media exhibiting effects such as dispersion[5-7], nonlinearity[8], anisotropy[9] and losses[10]. Such extensions have been carried out along with the development of efficient methods for obtaining nondiffracting beams and pulses in the subluminal, luminal and superluminal regimes[11-18]. This paper (partly a review) addresses some theoretical methods related to nondiffracting solutions of the linear wave equation in unbounded homogeneous media, as well as to some interesting applications of such waves. In section II we analyze the general structure of the Localized Waves, develop the so called Generalized Bidirectional Decomposition, and use it to obtain several luminal and superluminal (especially X-shaped) nondiffracting solutions of the wave equation. In section III we develop a space-time focusing method by a continuous superposition of X-Shaped pulses of different velocities. Section IV addresses the properties of chirped optical X-Shaped pulses propagating in material media without boundaries. Finally, in Section V, we show how a suitable superposition of Bessel beams can be used to obtain stationary localized wave fields, with a static envelope and a high transverse localization, and whose longitudinal intensity pattern can assume any desired shape within a chosen interval of the propagation axis.

physics.gen-ph↗
arXiv2007

Localized Waves: A scientific and historical introduction

In the first part of this paper (mainly a review) we present general and formal (simple) introductions to the ordinary gaussian waves and to the Bessel waves, by explicitly separating the cases of the beams from the cases of the pulses; and, finally, an analogous introduction is presented for the Localized Waves (LW), pulses or beams. Always we stress the very different characteristics of the gaussian with respect to the Bessel waves and to the LWs, showing the numerous and important properties of the latter w.r.t. the former ones: Properties that may find application in all fields in which an essential role is played by a wave-equation (like electromagnetism, optics, acoustics, seismology, geophysics, gravitation, elementary particle physics, etc.). In the second part of this paper (namely, in its Appendix), we recall at first how, in the seventies and eighties, the geometrical methods of Special Relativity (SR) had predicted --in the sense below specified-- the existence of the most interesting LWs, i.e., of the X-shaped pulses. At last, in connection with the circumstance that the X-shaped waves are endowed with Superluminal group-velocities (as carefully discussed in the first part of this article), we briefly mention the various experimental sectors of physics in which Superluminal motions seem to appear: In particular, a bird's-eye view is presented of the experiments till now performed with evanescent waves (and/or tunneling photons), and with the "localized Superluminal solutions" to the wave equations.

physics.gen-ph↗
arXiv2008

Chkareuli-Froggatt-Nielsen Theorem and Photon Mass

We analyze there is a relation between fossil charge and the mass of photon based on Chkareuli-Froggatt-Nielsen Theorem and Proca Lagrangian. As generally known, massive photon will lead to Lorentz non-invariance field theory.

physics.gen-ph↗
arXiv2007

The Physics of Information

We review of the interface between (theoretical) physics and information for non-experts. The origin of information as related to the notion of entropy is described, first in the context of thermodynamics then in the context of statistical mechanics. A close examination of the foundations of statistical mechanics and the need to reconcile the probabilistic and deterministic views of the world leads us to a discussion of chaotic dynamics, where information plays a crucial role in quantifying predictability. We then discuss a variety of fundamental issues that emerge in defining information and how one must exercise care in discussing concepts such as order, disorder, and incomplete knowledge. We also discuss an alternative form of entropy and its possible relevance for nonequilibrium thermodynamics. In the final part of the paper we discuss how quantum mechanics gives rise to the very different concept of quantum information. Entirely new possibilities for information storage and computation are possible due to the massive parallel processing inherent in quantum mechanics. We also point out how entropy can be extended to apply to quantum mechanics to provide a useful measurement for quantum entanglement. Finally we make a small excursion to the interface betweeen quantum theory and general relativity, where one is confronted with an "ultimate information paradox" posed by the physics of Black Holes. In this review we have limited ourselves; not all relevant topics that touch on physics and information could be covered.

physics.class-ph↗