Random Motion of a Charged Test Particle with a Classical Constant Velocity in Vacuum in a Cylindrical Spacetime

We examine the random motion of a charged test particle with a nonzero classical velocity driven by quantum electromagnetic vacuum fluctuations in a cylindrical spacetime and calculate both the velocity and position dispersions of the test particle. It is found that the dispersions display different behaviour in different directions. These differences can be understood as a result of the topology of the configuration and initial physical conditions.     

Semi-Classical Calculation of the Particle Production in QED via the Schwinger Dynamical Principle

The Schwinger quantum dynamical principle is used to calculate the free vacuum persistence amplitude in the presence of a prescribed electromagnetic background, and the probability that free pairs are created from the vacuum state. An explicit expression of these amplitudes is obtained in the semi-classical approach, showing that, in this approach, the particle production is a stochastic Poisson process. PACS subject classifications. 02.30.Xx, 11.15.Bt, 12.20.Ds, 12.20.-m.     

Investigation of the particle spin properties on the velocity space instability in high‐density plasmas

The nonresonant electromagnetic instabilities of the anisotropic velocity space (Weibel‐like) have always been one of the interesting subjects for researchers. These electromagnetic instabilities play an important role in generating strong magnetic fields in laboratory plasmas for applications such as inertial confinement fusion and space plasmas. In this paper, we investigate the quantum effects of the particle spin on the electromagnetic instabilities. In the case of the presence of a magnetic dipole force and an electron precession frequency like the Vlasov equation, we derive the full quantum equation. This study shows that, in the presence of the spin‐polarized effects, the growth rate of the instabilities is reduced compared to the classical cases and will not arise for low fractions of the temperature anisotropy for different values of the magnetic field. Indeed, it is expected that the probability of electron capture in the background magnetic fields and the effective collision with the particle increase because of the spin effect, so that a high portion of the electron energy is transmitted to the background plasma, and the temperature anisotropy governing the electron distribution is reduced.     

Dimension-dependent stimulated radiative interaction of a single electron quantum wavepacket

In the foundation of quantum mechanics, the spatial dimensions of electron wavepacket are understood only in terms of an expectation value – the probability distribution of the particle location. One can still inquire how the quantum electron wavepacket size affects a physical process. Here we address the fundamental physics problem of particle–wave duality and the measurability of a free electron quantum wavepacket. Our analysis of stimulated radiative interaction of an electron wavepacket, accompanied by numerical computations, reveals two limits. In the quantum regime of long wavepacket size relative to radiation wavelength, one obtains only quantum-recoil multiphoton sidebands in the electron energy spectrum. In the opposite regime, the wavepacket interaction approaches the limit of classical point-particle acceleration. The wavepacket features can be revealed in experiments carried out in the intermediate regime of wavepacket size commensurate with the radiation wavelength.     

Particle Creation in the Effective Action Method

The effect of particle creation by nonstationary external fields is considered as a radiation effect in the expectation-value spacetime. The energy of created massless particles is calculated as the vacuum contribution in the energy-momentum tensor of the expectation value of the metric. The calculation is carried out for an arbitrary quantum field coupled to all external fields entering the general second-order equation. The result is obtained as a functional of the external fields. The paper gives a systematic derivation of this result on the basis of the nonlocal effective action. Although the derivation is quite involved and touches on many aspects of the theory, the result itself is remarkably simple. It brings the quantum problem of particle creation to the level of complexity of the classical radiation problem. For external fields like the electromagnetic or gravitational field there appears a quantity, the radiation moment, that governs both the classical radiation of waves and the quantum particle production. The vacuum radiation of an electrically charged source is considered as an example. The research is aimed at the problem of backreaction of the vacuum radiation.     

Van der Waals force derived from a quantum statistical mechanical path integral method

The main purpose of this paper is to apply the quantum statistical mechanical model for polarizable fluids, used by Høye-Stell and others, to the calculation of the van der Waals force (dispersion force) between monatomics. The results are in agreement with those obtained by quantum perturbation theory. The quantum statistical method implies considerable formal simplifications.The introductory sections of the paper show, for illustrative purposes, how the dispersion forces in limiting cases also can be obtained from macroscopic quantum electromagnetic theory when two dilute dielectric media with plane-parallel surfaces are separated by a vacuum (Casimir effect).     

Quantum-Gravitational Diffusion and Stochastic Fluctuations in the Velocity of Light

We argue that quantum-gravitational fluctuations in the space-time background give the vacuum non-trivial optical properties that include diffusion and consequent uncertainties in the arrival times of photons, causing stochastic fluctuations in the velocity of light in vacuo. Our proposal is motivated within a Liouville string formulation of quantum gravity that also suggests a frequency-dependent refractive index of the particle vacuum. We construct an explicit realization by treating photon propagation through quantum excitations of D-brane fluctuations in the space-time foam. These are described by higher-genus string effects, that lead to stochastic fluctuations in couplings, and hence in the velocity of light. We discuss the possibilities of constraining or measuring photon diffusion in vacuo via -ray observations of distant astrophysical sources.     

各向异性磁电介质量子真空水平上的动量转移

通过计算各向异性磁电材料内电磁场模式的本征方程研究了任意方向量子真空模式对磁电材料动量转移总贡献，并指出介质由真空动量转移所获得速度可以由目前发展起来的光纤光学传感器(能测量纳米量级速度)所探测.对该量子真空宏观力学效应的物理机理与潜在应用也做了讨论.     

Gravity and the quantum vacuum inertia hypothesis

In previous work it has been shown that the electromagnetic quantum vacuum, or electromagnetic zero‐point field, makes a contribution to the inertial reaction force on an accelerated object. We show that the result for inertial mass can be extended to passive gravitational mass. As a consequence the weak equivalence principle, which equates inertial to passive gravitational mass, appears to be explainable. This in turn leads to a straightforward derivation of the classical Newtonian gravitational force. We call the inertia and gravitation connection with the vacuum fields the quantum vacuum inertia hypothesis . To date only the electromagnetic field has been considered. It remains to extend the hypothesis to the effects of the vacuum fields of the other interactions. We propose an idealized experiment involving a cavity resonator which, in principle, would test the hypothesis for the simple case in which only electromagnetic interactions are involved. This test also suggests a basis for the free parameter η(ν) which we have previously defined to parametrize the interaction between charge and the electromagnetic zero‐point field contributing to the inertial mass of a particle or object.     

Sculpting the vacuum in a photonic band gap micro-chip

We describe the engineering of the electromagnetic vacuum in a 2D–3D photonic bandgap (PBG) hetero-structure. This facilitates the development of novel active devices and the observation of novel quantum electrodynamic phenomena. We consider a specific architecture suitable as an all-optical micro-transistor capable of novel ultra-fast response with low switching power requirements. This relies on a unique collective atomic switching and population inversion achieved by coherent resonant pumping in a suitably engineered vacuum. Specific waveguide architectures within the 3D PBG micro-chip provide local density-of-states (LDOS) peaks near their cutoff frequency. These provide “building blocks” for electromagnetic vacuum engineering without recourse to conventional high Q-factor micro-cavities. For the all-optical micro-transistor, a fork shape LDOS within the micro-chip is desirable, using trimodal waveguide architecture. We delineate the functional robustness of these architectures to disorder caused by manufacturing errors within the PBG micro-chip.     

Anisotropic distribution of quantum‐vacuum momentum density in a moving electromagnetic medium

An isotropic electromagnetic medium becomes gyrotropically anisotropic when it moves, and an anisotropic electromagnetic environment can then be created in this motion‐induced anisotropic medium. One of the most remarkable features is that the quantum vacuum in the anisotropic electromagnetic environment exhibits a nonzero electromagnetic momentum density, since the universal symmetry of the vacuum fluctuation field is broken, and the anisotropic quantum vacuum mode structure is produced because of the symmetry breaking. This would give rise to a noncompensation effect among the four vacuum eigenmodes (i.e., the forward and backward propagating modes as well as their respective mutually perpendicular polarized components), and leads to an anisotropic correction to the vacuum momentum in the moving medium. The physical significance and the potential applications of the anisotropic quantum vacuum are discussed. This quantum‐vacuum effect may be used to develop sensitive sensor techniques and to design new quantum optical and photonic devices.     

Beyond the speed of light on Finsler spacetimes

As a prototypical massive field theory we study the scalar field on the recently introduced Finsler spacetimes. We show that particle excitations exist that propagate faster than the speed of light recognized as the boundary velocity of observers. This effect appears already in Finsler spacetime geometries with very small departures from Lorentzian metric geometry. It switches on for a sufficiently large ratio of the particle four-momentum and mass, and is the consequence of a modified version of the Coleman–Glashow velocity dispersion relation. The momentum dispersion relation on Finsler spacetimes is shown to be the same as on metric spacetimes, which differs from many quantum gravity models. If similar relations resulted for fermions on Finsler spacetimes, these generalized geometries could explain the potential observation of superluminal neutrinos claimed by the Opera Collaboration.     

Influence of Quantum Effects on the Magnetic Field Behavior in Overdense Plasma

We study the conditions for the anomalous transmission of electromagnetic waves through quantum overdense plasma. We show that this anomalous transmission is triggered due to the excitation of surface waves, as was observed in the classical overdense plasma. The conditions for the excitation of surface waves are obtained by studying the dispersion relation within the framework of quantum hydrodynamics. The corresponding consequences at the classical limits are consistent with the previous studies. In comparison with the classical regimes, the quantum dispersion curve exhibits an asymptotic behavior which indicates significant effects, in particular, at large wavelengths. Herein, to create the required evanescent waves, we consider the quantum plasma to be placed between two ordinary prisms and dielectrics. The effects of the main parameters, such as the permittivity of the prisms and dielectrics and the Fermi velocity, on the rate of the transmission and the magnetic field propagation are also evaluated.     

Thomson scattering induced by gravitational waves

We investigate the effects of a weak gravitational wave, modelled as a gaussian wavepacket, on the polarization state of an electromagnetic field enclosed in a cavity. Our approach is semiclassical, in that the electromagnetic field is described as a quantum field, while the gravitational perturbation is treated classically, as a slightly curved background spacetime. Assuming that before the interaction the electromagnetic field has been prepared in a given polarization state, we show that – due to the gravitational scattering with the wave – some photons having different polarization states are found in the cavity at late times. Such polarization scattering has some resemblance with Thomson scattering, well-known in Quantum Electrodynamics: hence the motivation for the title. We give a numerical estimate of the resulting photon polarization spreading in the case of a typical gravitational burst from a final supernova rebound. We also briefly comment about the possible influence of such gravitational scattering on the Cosmic Microwave Background (CMB) polarization.     

Spontaneous emission of the non-Wiener type

The spontaneous emission of a quantum particle and superradiation of an ensemble of identical quantum particles in a vacuum electromagnetic field with zero photon density are examined under the conditions of significant Stark particle and field interaction. New fundamental effects are established: suppression of spontaneous emission by the Stark interaction, an additional “decay” shift in energy of the decaying level as a consequence of Stark interaction unrelated to the Lamb and Stark level shifts, excitation conservation phenomena in a sufficiently dense ensemble of identical particles and suppression of superradiaton in the decay of an ensemble of excited quantum particles of a certain density. The main equations describing the emission processes under conditions of significant Stark interaction are obtained in the effective Hamiltonian representation of quantum stochastic differential equations. It is proved that the Stark interaction between a single quantum particle and a broadband electromagnetic field is represented as a quantum Poisson process and the stochastic differential equations are of the non-Wiener (generalized Langevin) type. From the examined case of spontaneous emission of a quantum particle, the main rules are formulated for studying open systems in the effective Hamiltonian representation.     

Random Motion of a Charged Test Particle with a Constant Classical Velocity in a Spacetime with a Plane Boundary

We study the random motion of a charged test particle coupled to electromagnetic vacuum fluctuations near a perfectly reflecting plane boundary with a nonzero classical constant velocity in a direction parallel to the plane. We calculate the mean squared fluctuations in the velocity and position of the test particle taking into account both fluctuating electric and magnetic forces. Our results show that the influence of fluctuating magnetic fields is, in general, of the higher order than that caused by fluctuating electric fields and is thus negligible.     

Lorentz Invariance and Brownian Motion of Test Particles with Constant Classical Velocity in Electromagnetic Vacuum

We show that the velocity and position dispersions of a test particle with a nonzero constant classical velocity undergoing Brownian motion caused by electromagnetic vacuum fluctuations in a space with plane boundaries can be obgained from those of the static case by Lorentz transformation. We explicitly derive the Lorentz transformations relating the dispersions of the two cases and then apply them to the case of the Brownian motion of a test particle with a constant classical velocity parallel to the boundary between two conducting planes. Our results show that the influence of a nonzero initial velocity is negligible for nonrelativistic test particles.