Abstract: Quantum effects in plasmas are of interest for a diverse set of systems, and have thus as a field been revived and attracted a lot of attention from a wide community over the past decade. In models of quantum plasmas, the effects studied mostly are due to the quantum particle dispersion and tunnelling. Such effects can be of importance in dense systems and on short length scales. There are also a number of effects related to spin and statistics. However, up to recently the magnetization effect in plasmas due to the intrinsic electron spin has been largely ignored. The magnetization dynamics of e. g. solids has many important applications, such as components for memory storage, but has also been discussed in more 'proper' plasma environments, such as fusion plasmas. Furthermore, also from a basic science point-of-view the effects of intrinsic spin and gyromagnetic effects are of considerable interest. Here we give a short review of a number of different models for treating magnetization effects in plasmas, with a focus on recent results. In particular, the transition between kinetic models and fluid models is discussed. We also give a number of examples of applications of such theories, as well as an outlook for possible future work.
Abstract: The nonlinear propagation of two-dimensional (2D) quantum ion-acoustic waves (QIAWs) is studied in a quantum electron-ion plasma. By using a 2D quantum hydrodynamic model and the method of multiple scales, a new set of coupled nonlinear partial differential equations is derived which governs the slow modulation of the 2D QIAW packets. The oblique modulational instability (MI) is then studied by means of a corresponding nonlinear Schrodinger equation derived from the coupled nonlinear partial differential equations. It is shown that the quantum parameter H (ratio of the plasmon energy density to Fermi energy) shifts the MI domains around the k theta-plane, where k is the carrier wave number and h is the angle of modulation. In particular, the ion-acoustic wave (IAW), previously known to be stable under parallel modulation in classical plasmas, is shown to be unstable in quantum plasmas. The growth rate of the MI is found to be quenched by the obliqueness of modulation. The modulation of 2D QIAW packets along the wave vector k is shown to be described by a set of Davey-Stewartson-like equations. The latter can be studied for the 2D wave collapse in dense plasmas. The predicted results, which could be important to look for stable wave propagation in laboratory experiments as well as in dense astrophysical plasmas, thus generalize the theory of MI of IAW propagations both in classical and quantum electron-ion plasmas. (C) 2011 American Institute of Physics. [doi:10.1063/1.3574913]
Abstract: The dynamics of an interface in a two-component Bose-Einstein condensate driven by a spatially uniform time-dependent force is studied. Starting from the Gross-Pitaevskii Lagrangian, the dispersion relation for linear waves and instabilities at the interface is derived by means of a variational approach. A number of diverse dynamical effects for different types of driving force is demonstrated, which includes the Rayleigh-Taylor instability for a constant force, the Richtmyer-Meshkov instability for a pulse force, dynamic stabilization of the Rayleigh-Taylor instability and onset of the parametric instability for an oscillating force. Gaussian Markovian and non-Markovian stochastic forces are also considered. It is found that the Markovian stochastic force does not produce any average effect on the dynamics of the interface, while the non-Markovian force leads to exponential perturbation growth.
Abstract: In this paper we calculate the contribution to the ponderomotive force in a plasma from the electron spin using a recently developed model. The spin-fluid model used in the present paper contains spin-velocity correlations, in contrast to previous models used for the same purpose. Is its then found that previous terms for the spin-ponderomotive force are recovered, but also that additional terms appear. Furthermore, the results due to the spin-velocity correlations are confirmed using the spin-kinetic theory. The significance of our results is discussed.
Abstract: The stability of a magnetic deflagration front in a media of molecular magnets, such as Mn-12 acetate, is considered. It is demonstrated that stationary deflagration is unstable with respect to one-dimensional perturbations if the energy barrier of the magnets is sufficiently high in comparison with the release of Zeeman energy at the front; their ratio may be interpreted as an analog to the Zeldovich number, as found in problems of combustion. When the Zeldovich number exceeds a certain critical value, a stationary deflagration front becomes unstable and propagates in a pulsating regime. Analytical estimates for the critical Zeldovich number are obtained. The linear stage of the instability is investigated numerically by solving the eigenvalue problem. The nonlinear stage is studied using direct numerical simulations. The parameter domain required for experimental observations of the pulsating regime is discussed.
Abstract: The dynamics of doping transformation fronts in organic semiconductor plasma is studied for application in light-emitting electrochemical cells. We show that new fundamental effects of the plasma dynamics can significantly improve the device performance. We obtain an electrodynamic instability, which distorts the doping fronts and increases the transformation rate considerably. We explain the physical mechanism of the instability, develop theory, provide experimental evidence, perform numerical simulations, and demonstrate how the instability strength may be amplified technologically. The electrodynamic plasma instability obtained also shows interesting similarity to the hydrodynamic Darrieus-Landau instability in combustion, laser ablation, and astrophysics.
Abstract: We study the dynamical Casimir effect in the presence of a finite coherence time, which is associated with a finite quality factor of the optical cavity. We use the time refraction model, where a fixed cavity with a modulated optical medium, replaces the empty cavity with a vibrating mirror. Temporal coherence is described with the help of cavity quasi-mode operators. Asymptotic expressions for the number of photon pairs generated from vacuum are derived. (C) 2011 Elsevier B.V. All rights reserved.
Abstract: The generation of attosecond pulses with an amplitude greatly exceeding the driving field of an ultrarelativistic laser pulse at oblique irradiation of a solid target is investigated. We develop a universal model of the process, the so-called relativistic electronic spring, which is different from the conventional concept of an oscillating mirror. It follows from the model that there exists a parameter region where the energy conversion from the femto- to the attosecond regime is maximal. Based on the study we propose a new concept of laser pulse interaction with a target having a groove-shaped surface, which opens up the potential to exceed an intensity level of 1026 W/cm(2) and observe effects due to nonlinear quantum electrodynamics with upcoming laser sources.
Abstract: Current high-intensity laser sources offer a multitude of research, experiment and application possibilities, ranging from e. g. ionisation studies of atomic and molecular systems to particle acceleration for medical purposes. Planned upgrades of existing laser sources will further increase the deliverable intensities and make certain low-intensity (as compared to the Schwinger field) tests of quantum electrodynamics viable. Moreover, secondary sources of radiation, and planned future facilities, offer several-orders-of-magnitude increases in intensities. Thus, it is highly relevant to ask what kind of physics that may be probed using future light sources.
Abstract: We derive the gauge-free Hamiltonian structure of an extended kinetic theory, for which the intrinsic spin of the particles is taken into account. Such a semi-classical theory can be of interest for describing, e.g., strongly magnetized plasma systems. We find that it is possible to construct a generalized noncanonical Poisson bracket on the extended phase space, and discuss the implications of our findings, including stability of monotonic equilibria. (C) 2011 Elsevier B.V. All rights reserved.
Abstract: We investigate strong field vacuum effects using a phase-space approach based on the Wigner formalism. We calculate the Wigner function in a strong null-field background exactly, using lightfront field theory. The Wigner function exhibits the distinct features of strong field QED: in particular, we identify the effective mass in a laser pulse, compare it to the well-known mass shift in a periodic plane wave and identify signals of multiphoton absorption and emission. Finally, we show how to extend our results to describe vacuum pair production in colliding laser pulses.
Abstract: A coated hollow core microsphere is introduced as a novel target in ultra-intense laser-matter interaction experiments. In particular, it facilitates staged laser-driven proton acceleration by combining conventional target normal sheath acceleration (TNSA), power recycling of hot laterally spreading electrons and staging in a very simple and cheap target geometry. During TNSA of protons from one area of the sphere surface, laterally spreading hot electrons form a charge wave. Due to the spherical geometry, this wave refocuses on the opposite side of the sphere, where an opening has been laser micromachined. This leads to a strong transient charge separation field being set up there, which can post-accelerate those TNSA protons passing through the hole at the right time. Experimentally, the feasibility of using such targets is demonstrated. A redistribution is encountered in the experimental proton energy spectra, as predicted by particle-in-cell simulations and attributed to transient fields set up by oscillating currents on the sphere surface.
Abstract: The gauge invariant electromagnetic Wigner equation is taken as the basis of a fluid-like system describing quantum plasmas, derived from the moments of the gauge invariant Wigner function. The use of the standard, gauge-dependent Wigner function is shown to produce inconsistencies if a direct correspondence principle is applied. The propagation of linear transverse waves is considered and it is shown to be in agreement with the kinetic theory in the long-wavelength approximation, provided that an adequate closure is chosen for the macroscopic equations. A general recipe to solve the closure problem is suggested.
Abstract: We discuss various limits which transform configuration space into phase space, with emphasis on those related to lightfront field theory, and show that they are unified by spectral flow. Examples include quantising in â€almost lightfront’ coordinates and the appearance of lightlike noncommutativity from a strong background laser field. We compare this with the limit of a strong magnetic field, and investigate the role played by lightfront zero modes.
Abstract: We review the effects of strong background fields in noncommutative QED. Beginning with the noncommutative Maxwell and Dirac equations, we describe how combined noncommutative and strong field effects modify the propagation of fermions and photons. We extend these studies beyond the case of constant backgrounds by giving a new and revealing interpretation of the photon dispersion relation. Considering scattering in background fields, we then show that the noncommutative photon is primarily responsible for generating deviations from strong field QED results. Finally, we propose a new method for constructing gauge invariant variables in noncommutative QED, and use it to analyse the physics of our null background fields.
Abstract: The nonlinear interaction between electromagnetic, electrostatic and gravitational waves in a Vlasov plasma is reconsidered. By using a orthonormal tetrad description the three-wave coupling coefficients are computed. Comparing with previous results, it is found that the present theory leads to algebraic expression that are much reduced, as compared to those computed using a coordinate frame formalism. Furthermore, here we calculate the back reaction on the gravitational waves, and a simple energy conservation law is deduced in the limit of a cold plasma.
Abstract: We consider high field physics due to quantum electrodynamics, in particular those that can be studied in the next generation of laser facilities. Effective field theories based on the Euler-Heisenberg Lagrangian are briefly reviewed, and examples involving plasma- and vacuum physics are given.
Abstract: The nonlinear propagation of electromagnetic (EM) electron-cyclotron waves (whistlers) along an external magnetic field, and their modulation by electrostatic small but finite amplitude ion-acoustic density perturbations are investigated in a uniform quantum plasma with intrinsic spin of electrons. The effects of the quantum force associated with the Bohm potential and the combined effects of the classical as well as the spin-induced ponderomotive forces (CPF and SPF, respectively) are taken into consideration. The latter modify the local plasma density in a self-consistent manner. The coupled modes of wave propagation is shown to be governed by a modified set of nonlinear Schrödinger-Boussinesq-like equations which admit exact solutions in form of stationary localized envelopes. Numerical simulation reveals the existence of large-scale density fluctuations that are self-consistently created by the localized whistlers in a strongly magnetized high density plasma. The conditions for the modulational instability (MI) and the value of its growth rate are obtained. Possible applications of our results, e.g., in strongly magnetized dense plasmas and in the next generation laser-solid density plasma interaction experiments are discussed.
Abstract: We derive a fluid theory for spin-1/2 particles starting from an extended kinetic model based on a spin-projected density matrix formalism. The evolution equation for the spin density is found to contain a pressurelike term. We give an example where this term is important by looking at a linear mode previously found in a spin kinetic model.
Abstract: The excitation of electrostatic wakefields in a magnetized spin quantum plasma by the classical and the spin-induced ponderomotive force (CPF and SPF, respectively) due to whistler waves is reported. The nonlinear dynamics of the whistlers and the wakefields is shown to be governed by a coupled set of nonlinear Schrödinger and driven Boussinesq-like equations. It is found that the quantum force associated with the Bohm potential introduces two characteristic length scales, which lead to the excitation of multiple wakefields in a strongly magnetized dense plasma (with a typical magnetic field strength B0≳109 T and particle density n0≳1036 mâ’3), where the SPF strongly dominates over the CPF. In other regimes, namely, B0≲108 T and n0≲1035 mâ’3, where the SPF is comparable to the CPF, a plasma wakefield can also be excited self-consistently with one characteristic length scale. Numerical results reveal that the wakefield amplitude is enhanced by the quantum tunneling effect; however, it is lowered by the external magnetic field. Under appropriate conditions, the wakefields can maintain high coherence over multiple plasma wavelengths and thereby accelerate electrons to extremely high energies. The results could be useful for particle acceleration at short scales, i.e., at nanometer and micrometer scales, in magnetized dense plasmas where the driver is the whistler wave instead of a laser or a particle beam.
Abstract: The appearance of rogue waves is well known in oceanographics, optics, and cold matter systems. Here we show a possibility for the existence of atmospheric rogue waves.
Abstract: Starting from the Pauli Hamiltonian operator, we derive scalar quantum kinetic equations for spin-1/2 systems. Here, the regular Wigner two-state matrix is replaced by a scalar distribution function in extended phase space. Apart from being a formulation of significant interest, such a scalar quantum kinetic equation makes the comparison with classical kinetic theory straightforward and lends itself naturally to currently available numerical Vlasov and Boltzmann schemes. Moreover, while the quasi-distribution is a Wigner function in regular phase space, it is given by a Q-function in spin space. As such, nonlinear and dynamical quantum plasma problems are readily handled. Moreover, the issue of gauge invariance is treated.
Abstract: We show the possible excitation of a phonon laser instability in an ultra-cold atomic gas confined in a magneto-optical trap. Such an effect results from a negative Landau damping of the collective density perturbations in the gas, leading to the coherent emission of phonons. This laser instability can be driven by a blue-detuned laser superimposed to the usual red-detuning laser beams which usually provide the cooling mechanism. Threshold conditions, instability growth rates and saturation levels are derived. This work generalizes, on theoretical grounds, the recent results obtained with a single-ion phonon laser, to an ultra-cold atomic gas, where real phonons can be excited. Future phonon lasers could thus adequately be called phasers. Copyright (c) EPLA, 2010
Abstract: We develop a model describing the electrochemical conversion of an organic semiconductor (specifically, the active material in a light-emitting electrochemical cell) from the undoped nonconducting state to the doped conducting state. The model, an extended Nernst-Planck-Poisson model, takes into account both strongly concentration-dependent mobility and diffusion for the electronic charge carriers and the Nernst equation in the doped conducting regions. The standard Nernst-Planck-Poisson model is shown to fail in its description of the properties of the doping front. Solving our extended model numerically, we demonstrate that doping front progression in light-emitting electrochemical cells can be accurately described.
Abstract: Through an extended kinetic model, we study the nonlinear generation of quasi-static magnetic fields by high-frequency fields in a plasma, taking into account the effects of the electron spin. It is found that although the largest part of the nonlinear current in a moderate density, moderate temperature plasma is due to the classical terms, the spin may still give a significant contribution to the magnetic field generation mechanism. Applications of our results are discussed.
Abstract: A set of quantum hydrodynamic equations are derived from the moments of the electrostatic mean-field Wigner kinetic equation. No assumptions are made on the particular local equilibrium or on the statistical ensemble wave functions. Quantum diffraction effects appear explicitly only in the transport equation for the heat flux triad, which is the third-order moment of the Wigner pseudo-distribution. The general linear dispersion relation is derived, from which a quantum modified Bohm-Gross relation is recovered in the long wave-length limit. Nonlinear, traveling wave solutions are numerically found in the one-dimensional case. The results shed light on the relation between quantum kinetic theory, the Bohm-de Broglie-Madelung eikonal approach, and quantum fluid transport around given equilibrium distribution functions. (C) 2009 Elsevier B.V. All rights reserved.
Abstract: We discuss a twofold extension of QED assuming the presence of strong external fields provided by an ultraintense laser and noncommutativity of spacetime. While noncommutative effects leave the electron’s intensity induced mass shift unchanged, photons change significantly in character: they acquire a quasimomentum that is no longer lightlike. We study the consequences of this combined noncommutative strong-field effect for the basic lepton-photon interactions.
Abstract: The influence of the intrinsic spin of electrons on the propagation of circularly polarized waves in a magnetized plasma is considered. New eigenmodes are identified, one of which propagates below the electron cyclotron frequency, one above the spin-precession frequency, and another close to the spin-precession frequency. The latter corresponds to the spin modes in ferromagnets under certain conditions. In the non-relativistic motion of electrons, the spin effects become noticeable even when the external magnetic field B0 is below the quantum critical magnetic field strength, i.e. B0 < BQ = 4.4138×10^9 T and the electron density satisfies n0 >> nc ≠10^32 m^â’3. The importance of electron spin (paramagnetic) resonance (ESR) for plasma diagnostics is discussed.
Abstract: The influence of electron spin on the nonlinear propagation of whistler waves is studied in this paper. For this purpose, a recently developed electron two-fluid model, where the spin-up and spin-down populations are treated as different fluids, is adapted to the electron magnetohydrodynamic (MHD) regime. A nonlinear Schrodinger equation is then derived for the whistler waves and the coefficients of nonlinearity with and without spin effects are compared. The relative importance of spin effects depends on the plasma density and temperature as well as the external magnetic field strength and wave frequency. The significance of our results for various plasmas is discussed.
Abstract: We consider stimulated pair production employing strong-field QED in a high-intensity laser background. In an infinite plane wave, we show that light-cone quasi-momentum can only be transferred to the created pair as a multiple of the laser frequency, i.e. by a higher harmonic. This translates into discrete resonance conditions providing the support of the pair creation probability which becomes a delta-comb. These findings corroborate the usual interpretation of multi-photon production of pairs with an effective mass. In a pulse, the momentum transfer is continuous, leading to broadening of the resonances and sub-threshold behaviour. The peaks remain visible as long as the number of cycles per pulse exceeds unity. The resonance patterns in pulses are analogous to those of a diffraction process based on interference of the produced pairs. We finally comment on the dependence of the peak positions, and in turn the effective mass, on the pulse shape.
Abstract: The concept of a ponderomotive force due to the intrinsic spin of electrons is developed. An expression containing both the classical as well as the spin-induced ponderomotive force is derived. The results are used to demonstrate that an electromagnetic pulse can induce a spin-polarized plasma. Furthermore, it is shown that, for certain parameters, the nonlinear backreaction on the electromagnetic pulse from the spin magnetization current can be larger than that from the classical free current. Suitable parameter values for a direct test of this effect are presented.
Abstract: Themagnetically induced Richtmyer-Meshkov (RM) instability in a two-component Bose-Einstein condensate (BEC) is investigated. We construct and study analytical models describing the development of the instability at both the linear and nonlinear stages. The models indicate interesting features of the instability: surface tension implies departure from the linear growth of modes and separation of droplets, which are qualitatively different from the traditional RM case of classical gases, and the trapping potential affects the later stages of the instability. We perform numerical simulations of the instability in a trapped BEC using the Gross-Pitaevskii equation and compare the simulation results to the model predictions.
Abstract: The capability to produce high field strengths, and thereby obtain a new means for doing fundamental physics, has over the last thirty years taken great leaps forward. Both superconducting cavities as well ultra-intense lasers can now reach field strengths of the order 50 MV/m (stationary) and 10(12) V/m (peak value, time-dependent field), respectively. Here we will describe a collection of problems that catches the flavor of the nonlinear quantum vacuum and the possibility to use high field strengths as a low-energy probe of fundamental physics.
Abstract: The main characteristics of the linear Darrieus-Landau instability in the laser ablation flow are investigated. The dispersion relation of the instability is found numerically as a solution to an eigenvalue stability problem, taking into account the continuous structure of the flow. The results are compared to the classical Darrieus-Landau instability of a usual slow flame. The difference between the two cases is due to the specific features of laser ablation: sonic velocities of hot plasma and strong temperature dependence of thermal conduction. It is demonstrated that the Darrieus-Landau instability in laser ablation is much stronger than in the classical case. In particular, the maximum growth rate in the case of laser ablation is about three times larger than that for slow flames. The characteristic length scale of the Darrieus-Landau instability in the ablation flow is comparable to the total distance from the ablation zone to the critical zone of laser light absorption. The possibility of experimental observations of the Darrieus-Landau instability in laser ablation is discussed.
Abstract: We present a theoretical investigation of the excitation of multiple electrostatic wakefields by the ponderomotive force of a short electromagnetic pulse propagating through a dense plasma. It is found that the inclusion of the quantum statistical pressure and quantum electron tunneling effects can qualitatively change the classical behavior of the wakefield. In addition to the well-known plasma oscillation wakefield, with a wavelength of the order of the electron skin depth (lambda(e) = c/omega(pe), which in a dense plasma is of the order of several nanometers, where c is the speed of light in vacuum and omega(pe) is the electron plasma frequency), wakefields in dense plasmas with a shorter wavelength (in comparison with lambda(e)) are also excited. The wakefields can trap electrons and accelerate them to extremely high energies over nanoscales. (C) 2009 Elsevier B.V. All rights reserved.
Abstract: The quantum vacuum constitutes a fascinating medium of study, in particular since near-future laser facilities will be able to probe the nonlinear nature of this vacuum. There has been a large number of proposed tests of the low-energy, high intensity regime of quantum electrodynamics (QED) where the nonlinear aspects of the electromagnetic vacuum come into play, and we will here give a short description of some of these. Such studies can shed light, not only on the validity of QED, but also on certain aspects of nonperturbative effects, and thus also give insights for quantum field theories in general.
Abstract: We investigate influence of magnetic field on the Rayleigh-Taylor instability in quantum plasmas with para- and ferromagnetic properties. Magnetization of quantum plasma happens due to the collective electron spin behavior at low temperature and high plasma density. In the classical case, without magnetization, magnetic field tends to stabilize plasma perturbations with wave numbers parallel to the field and with sufficiently short wavelengths. Paramagnetic effects in quantum plasma make this stabilization weaker. The stabilization disappears completely for short wavelength perturbations in the ferromagnetic limit, when the magnetic field is produced by intrinsic plasma magnetization only. Still, for perturbations of long and moderate wavelength, certain stabilization always takes place due to the nonlinear character of quantum plasma magnetization.
Abstract: Large-amplitude water waves on deep water have long been known in the seafaring community, and are the cause of great concern for, e. g., oil platform constructions. The concept of such freak waves is nowadays, thanks to satellite and radar measurements, well established within the scientific community. There are a number of important models and approaches for the theoretical description of such waves. By analyzing the scaling behavior of freak wave formation in a model of two interacting waves, described by two coupled non-linear Schrodinger equations, we show that there are two different dynamical scaling behaviors above and below a critical angle theta(c) of the direction of the interacting waves, below which all wave systems evolve and display statistics similar to a wave system of non-interacting waves. The results equally apply to other systems described by the non-linear Schrodinger equations, and should be of interest when designing optical wave guides. Copyright (C) EPLA, 2009
Abstract: The capability to produce high field strengths, and thereby obtain a new means for doing fundamental physics, has over the last thirty years taken great leaps forward. Both superconducting cavities as well ultra-intense lasers can now reach field strengths of the order 50 MV/m (stationary) and 10(12) V/m (peak value, time-dependent field), respectively. Here we will describe a collection of problems that catches the flavor of the nonlinear quantum vacuum and the possibility to use high field strengths as a low-energy probe of fundamental physics.
Abstract: In this work a recently published semiclassical spin kinetic model, generalizing those of previous authors are discussed. Some previously described properties are reviewed, and a new example illustrating the theory is presented. The generalization to a fully quantum mechanical description is discussed, and the main features of such a theory is outlined. Finally, the main conclusions are presented.
Abstract: In this work a recently published semiclassical spin kinetic model, generalizing those of previous authors are discussed. Some previously described properties are reviewed, and a new example illustrating the theory is presented. The generalization to a fully quantum mechanical description is discussed, and the main features of such a theory is outlined. Finally, the main conclusions are presented.
Abstract: By using the quantum hydrodynamic and Maxwell equations, we derive the generalized nonlinear electron magnetohydrodynamic, the generalized nonlinear Hall-MHD (HMHD), and the generalized nonlinear dust HMHD equations in a self-gravitating dense magnetoplasma. Our nonlinear equations include the self-gravitating, the electromagnetic, the quantum statistical electron pressure, as well as the quantum electron tunneling and electron spin forces. They are useful for investigating a number of wave phenomena including linear and nonlinear electromagnetic waves, as well as three-dimensional electromagnetic wave turbulence spectra and structures arising from mode coupling processes at nanoscales in dense quantum magnetoplasmas.
Abstract: We consider a dusty plasma where dust particles have a magnetic dipole moment. A Hall-MHD type of model, generalized to account for the intrinsic magnetization, is derived. The model is shown to be energy conserving, and the energy density and flux are derived. The general dispersion relation is then derived, and we show that kinetic dust-Alfven waves exhibit instability for a low dust and ion temperature and high dust density. We discuss the implication of our results.
Abstract: The Jeans instability is analyzed for dense magnetohydrodynamic plasmas with intrinsic magnetization, the latter due to collective electron spin effects. Furthermore, the effects of electron tunneling as well as the Fermi pressure are included. It is found that the intrinsic magnetization of the plasma will enhance the Jeans instability, and can significantly modify the structure of the instability spectra. Implications and limitations of our results are discussed, as well as possible generalizations. (C) 2008 American Institute of Physics.
Abstract: Tunneling of microwaves through a smooth barrier in a transmission line is considered. In contrast to standard wave barriers, we study the case where the dielectric permittivity is positive, and the barrier is caused by the inhomogeneous dielectric profile. It is found that reflectionless, superluminal tunneling can take place for waves with a finite spectral width. The consequences of these findings are discussed, and an experimental setup testing our predictions is proposed.
Abstract: A kinetic theory for spin plasmas is put forward, generalizing those of previous authors. In the model, the ordinary phase space is extended to include the spin degrees of freedom. Together with Maxwell’s equations, the system is shown to be energy conserving. Analyzing the linear properties, it is found that new types of wave-particle resonances are possible that depend directly on the anomalous magnetic moment of the electron. As a result, new wave modes, not present in the absence of spin, appear. The implications of our results are discussed.
Abstract: The fluid theory of plasmas is extended to include the properties of electron spin. The linear theory of waves in a magnetized plasma is presented, and it is shown that the spin effects cause a change of the magnetic permeability. Furthermore, by changing the direction of the external magnetic field, the magnetic permeability may become negative. This leads to instabilities in the long wavelength regimes. If these can be controlled, however, the spin plasma becomes a metamaterial for a broad range of frequencies, i.e. above the ion cyclotron frequency but below the electron cyclotron frequency. The consequences of our results are discussed.
Abstract: Surface plasmon polaritons (SPPs) have recently been recognized as an important future technique for microelectronics. Such SPPs have been studied using classical theory. However, current state-of-the-art experiments are rapidly approaching nanoscales, and quantum effects can then become important. Here we study the properties of quantum SPPs at the interface between an electron quantum plasma and a dielectric material. It is shown that the effect of quantum broadening of the transition layer is most important. In particular, the damping of SPPs does not vanish even in the absence of collisional dissipation, thus posing a fundamental size limit for plasmonic devices. Consequences and applications of our results are pointed out. Copyright (C) EPLA, 2008
Abstract: The role of viscous stress in heating of the fuel mixture in deflagration-to-detonation transition in tubes is studied both analytically and numerically. The analytical theory is developed in the limit of low Mach number; it determines temperature distribution ahead of an accelerating flame with maximum achieved at the walls. The heating effects of viscous stress and the compression wave become comparable at sufficiently high values of the Mach number. In the case of relatively large Mach number, viscous heating is investigated by direct numerical simulations. The simulations were performed on the basis of compressible Navier-Stokes gas-dynamic equations taking into account chemical kinetics. In agreement with the theory, viscous stress makes heating and explosion of the fuel mixture preferential at the walls. The explosion develops in an essentially multi-dimensional way, with fast spontaneous reaction spreading along the walls and pushing inclined shocks. Eventually, the combination of explosive reaction and shocks evolves into detonation. (C) 2008 Elsevier B.V. All rights reserved.
Abstract: The existence of magnetosonic solitons in dusty plasmas is investigated. The nonlinear magnetohydrodynamic equations for a warm dusty magnetoplasma are thus derived. A solution of the nonlinear equations is presented. It is shown that, owing to the presence of dust, static structures are allowed. This is in sharp contrast to the formation of the so-called shocklets in usual magnetoplasmas. A comparatively small number of dust particles can thus drastically alter the behavior of the nonlinear structures in magnetized plasmas.
Abstract: The nonlinear propagation of a circularly polarized electromagnetic (CPEM) wave in a strongly magnetized electron-positron-ion plasma is investigated. Two coupled equations describing the interaction between a high-frequency CPEM wave and the low-frequency electrostatic wake field are derived. It is found that the generation of the wake fields partly depends on the presence of the ion species and the external magnetic field. The wake field generation in turn leads to deceleration and frequency down conversion of the electromagnetic pulse. (C) 2008 American Institute of Physics.
Abstract: Two different quantum processes are considered in a perturbed vacuum cavity: time refraction and dynamical Casimir effect. They are shown to be physically equivalent, and are predicted to be unstable, leading to an exponential growth in the number of photons created in the cavity. The concept of an effective Unruh acceleration for these processes is also introduced, in order to make a comparison in terms of radiation efficiency, with the Unruh radiation associated with an accelerated frame in unbounded vacuum. (C) 2008 Elsevier B.V. All rights reserved.
Abstract: Influence of quantum effects on the internal waves and the Rayleigh-Taylor instability in plasma is investigated. It is shown that quantum pressure always stabilizes the RT instability. The problem is solved both in the limit of short-wavelength perturbations and exactly for density profiles with layers of exponential stratification. In the case of stable stratification, quantum pressure modifies the dispersion relation of the inertial waves. Because of the quantum effects, the internal waves may propagate in the transverse direction, which was impossible in the classical case. A specific form of pure quantum internal waves is obtained, which do not require any external gravitational field. (c) 2008 Elsevier B.V. All rights reserved.
Abstract: The problem of the Darrieus-Landau instability at a discontinuous deflagration front in a compressible flow is solved. Numerous previous attempts to solve this problem suffered from the deficit of boundary conditions. Here, the required additional boundary condition is derived rigorously taking into account the internal structure of the front. The derived condition implies a constant mass flux at the front; it reduces to the classical Darrieus-Landau condition in the limit of an incompressible flow. It is demonstrated that in general the solution to the problem depends on the type of energy source in the flow. In the common case of a strongly localized source, compression effects make the Darrieus-Landau instability considerably weaker. Particularly, the instability growth rate is reduced for laser ablation in comparison to the classical incompressible case. The instability disappears completely in the Chapman-Jouguet regime of ultimately fast deflagration. (C) 2008 American Institute of Physics.
Abstract: The three-dimensional instability of two coupled electromagnetic waves in an unmagnetized plasma is investigated theoretically and numerically. In the regime of two-plasmon decay, where one pump wave frequency is approximately twice the electron plasma frequency, we find that the coupled pump waves give rise to enhanced instability with wavevectors between those of the two beams. In the case of ion parametric decay instability, where the pump wave decays into one Langmuir wave and one ion acoustic wave, the instability regions are added with no distinct amplification. Our investigation can be useful in interpreting laser-plasma as well as ionospheric heating experiments.
Abstract: The structure of a weak shock in a quantum plasma is studied, taking into account both dissipation terms due to thermal conduction and dispersive quantum terms due to the Bohm potential. Unlike quantum systems without dissipations, even a small thermal conduction may lead to a stationary shock structure. In the limit of zero quantum effects, the monotonic Burgers solution for the weak shock is recovered. Still, even small quantum terms make the structure nonmonotonic with the shock driving a train of oscillations into the initial plasma. The oscillations propagate together with the shock. The oscillations become stronger as the role of Bohm potential increases in comparison with thermal conduction. The results could be of importance for laser-plasma interactions, such as inertial confinement fusion plasmas, and in astrophysical environments, as well as in condensed matter systems. (C) 2008 American Institute of Physics.
Abstract: Quantum electrodynamics predicts that photons undergo one-loop scattering. The combined effect of this on the behaviour of a photon gas for temperatures above similar to 10(10) K results in a softening of the equation of state. We calculate the effect this has on the effective equation of state in the early universe, taking into account all the species of the Standard Model. The change to the dynamics of the early universe is discussed. (c) 2007 Elsevier B.V. All rights reserved.
Abstract: For quantum effects to be significant in plasmas it is often assumed that the temperature over density ratio must be small. In this paper we challenge this assumption by considering the contribution to the dynamics from the electron spin properties. As a starting point we consider a multicomponent plasma model, where electrons with spin-up and spin-down are regarded as different fluids. By studying the propagation of Alfven wave solitons we demonstrate that quantum effects can survive in a relatively high-temperature plasma. The consequences of our results are discussed.
Abstract: The structure of spacetime, quantum field theory, and thermodynamics are all connected through the concepts of the Hawking and Unruh temperatures. The possible detection of the related radiation constitutes a fundamental test of such subtle connections. Here a scheme is presented for the detection of Unruh radiation based on currently available laser systems. By separating the classical radiation from the Unruh response in frequency space, it is found that the detection of Unruh radiation is possible in terms of soft x-ray photons using current laser-electron beam technology. The experimental constraints are discussed and a proposal for an experimental design is given.
Abstract: Here we respond to the comment by Tsagas on our earlier paper. We show that the results in that comment are flawed and cannot be used for drawing conclusions about the nature of magnetic field amplification by gravitational waves and give further support that the results of our earlier paper are correct.
Abstract: We present for the first time the nonlinear dynamics of quantum electrodynamic (QED) photon splitting in a strongly magnetized electron-positron (pair) plasma. By using a QED corrected Maxwell equation, we derive a set of equations that exhibit nonlinear couplings between electromagnetic (EM) waves due to nonlinear plasma currents and QED polarization and magnetization effects. Numerical analyses of our coupled nonlinear EM wave equations reveal the possibility of a more efficient decay channel, as well as new features of energy exchange among the three EM modes that are nonlinearly interacting in magnetized pair plasmas. Possible applications of our investigation to astrophysical settings, such as magnetars, are pointed out.
Abstract: The modulational instability of nonlinearly interacting spatially incoherent Stokes waves is analyzed. Starting from a pair of nonlinear Schrodinger equations, we derive a coupled set of wave-kinetic equations by using the Wigner transform technique. It is shown that the partial coherence of the interacting waves induces novel effects on the dynamics of crossing sea states.
Abstract: The theory for large amplitude circularly polarized waves propagating along an external magnetic field is extended in order to also include vacuum polarization effects. A general dispersion relation, which unites previous results, is derived. (c) 2007 American Institute of Physics.
Abstract: The fully nonlinear governing equations for spin-(1)/(2) quantum plasmas are presented. Starting from the Pauli equation, the relevant plasma equations are derived, and it is shown that nontrivial quantum spin couplings arise, enabling studies of the combined collective and spin dynamics. The linear response of the quantum plasma in an electron-ion system is obtained and analyzed. Applications of the theory to solid state and astrophysical systems as well as dusty plasmas are pointed out.
Abstract: A set of fluid equations, taking into account the spin properties of the electrons and positrons in a magnetoplasma, are derived. The magnetohydrodynamic limit of the pair plasma is investigated. It is shown that the microscopic spin properties of the electrons and positrons can lead to interesting macroscopic and collective effects in strongly magnetized plasmas. In particular, it is found that new Alfvenic solitary structures, governed by a modified Korteweg-de Vries equation, are allowed in such plasmas. These solitary structures vanish if the quantum spin effects are neglected. Our results should be of relevance for astrophysical plasmas, e.g., in pulsar magnetospheres, as well as for low-temperature laboratory plasmas. (C) 2007 American Institute of Physics.
Abstract: Starting from the governing equations for a quantum magnetoplasma including the quantum Bohm potential and electron spin-1/2 effects, we show that the system of quantum magnetohydrodynamic (QMHD) equations admits rarefactive solitons due to the balance between nonlinearities and quantum diffraction and tunneling effects. It is found that the electron spin-1/2 effect introduces a pressurelike term with negative sign in the QMHD equations, which modifies the shape of the solitary magnetosonic waves and makes them wider and shallower. Numerical simulations of the time-dependent system shows the development of rarefactive QMHD solitary waves that are modified by the spin effects.
Abstract: We consider a low-temperature plasma within a newly developed magnetohydrodynamic fluid model. In addition to the standard terms, the electron spin, quantum particle dispersion, and degeneracy effects are included. It turns out that the electron spin properties can give rise to ferromagnetic behavior in certain regimes. If additional conditions are satisfied, a homogeneous magnetized plasma can even be unstable. This happens in the low-temperature high-density regime, when the magnetic properties associated with the spin can overcome the stabilizing effects of the thermal and Fermi pressure, to cause a Jeans-like instability.
Abstract: Starting from the non-relativistic Pauli description of spin-1/2 particles, a set of fluid equations, governing the dynamics of such particles interacting with external fields and other particles, is derived. The equations describe electrons, positrons, holes and similar conglomerates. In the case of electrons, the magnetohydrodynamic limit of an electron-ion plasma is investigated. The results should be of interest and relevance both to laboratory and astrophysical plasmas.
Abstract: The quantum electrodynamical (QED) short wavelength correction on plasma wave propagation for a nonrelativistic quantum plasma is investigated. A general dispersion relation for a thermal multicomponent quantum plasma is derived. It is found that the classical dispersion relation for any wave mode can be modified to include quantum and short wavelength QED effects by simple substitutions of the thermal velocity and the plasma frequency. Furthermore, the dispersion relation has been modified to include QED effects of strong magnetic fields. It is found that strong magnetic fields together with the short wavelength QED correction will induce dispersion both in vacuum and in otherwise nondispersive plasma modes. Applications to laboratory and astrophysical systems are discussed. (c) 2007 American Institute of Physics.
Abstract: The nonlinear interaction between two laser beams in a plasma is investigated in the weakly nonlinear and relativistic regime. The evolution of the laser beams is governed by two nonlinear Schrodinger equations that are coupled with the slow plasma density response. A nonlinear dispersion relation is derived and used to study the growth rates of the Raman forward and backward scattering instabilities as well of the Brillouin and self-focusing/modulational instabilities. The nonlinear evolution of the instabilities is investigated by means of direct simulations of the time-dependent system of nonlinear equations. (c) 2006 American Institute of Physics.
Abstract: A kinetic theory for electromagnetic ion waves in a cold relativistic plasma is derived. The kinetic equation for the broadband electromagnetic ion waves is coupled to the slow density response via an acoustic equation driven by a ponderomotive force-like term linear in the electromagnetic field amplitude. The modulational instability growth rate is derived for an arbitrary spectrum of waves. The monochromatic and random phase cases are studied. A kinetic theory for electromagnetic ion waves in a cold relativistic plasma is derived. The kinetic equation for the broadband electromagnetic ion waves is coupled to the slow density response via an acoustic equation driven by a ponderomotive force-like term linear in the electromagnetic field amplitude. The modulational instability growth rate is derived for an arbitrary spectrum of waves. The monochromatic and random phase cases are studied. (c) 2006 American Institute of Physics.
Abstract: The statistical properties of the Salerno model are investigated. In particular, a comparison between the coherent and partially coherent wave modes is made for the case of a random-phased wave packet. It is found that the random-phased-induced spectral broadening gives rise to the damping of instabilities, but also a broadening of the instability region in quasiparticle momentum space. The results can be of significance for the condensation of magnetic-moment bosons in deep optical lattices.
Abstract: We present an investigation of nonlinear interactions between gravitational radiation and modified Alfven modes in astrophysical dusty plasmas. Assuming that stationary charged dust grains form neutralizing background in an electron-ion-dust plasma, we obtain the three-wave coupling coefficients and calculate the growth rates for parametrically coupled gravitational radiation and modified Alfven-Rao modes. The threshold value of the gravitational wave amplitude associated with convective stabilization is particularly small if the gravitational frequency is close to twice the modified Alfven wave frequency. The implication of our results to astrophysical dusty plasmas is discussed.
Abstract: The effects of partial coherence on the propagation of dispersive Alfven waves in a magnetoplasma are investigated. In particular, nonlinear interactions between dispersive Alfven waves and ion-acoustic perturbations are considered by means of a Wigner formalism. A set of governing equations consisting of a kinetic equation for dispersive Alfven waves coupled nonlinearly to a ponderomotive force driven ion-acoustic wave equation is obtained. The governing nonlinear equations are used to derive a nonlinear dispersion relation that is appropriate for investigating the modulational instability of broadband Alfven wavepackets. The spectral broadening of the Alfven waves gives rise to new regimes for the growth rate of the modulational instability.
Abstract: A kinetic equation describing the nonlinear evolution of intense electromagnetic pulses in electron-positron (e-p) plasmas is presented. The modulational instability is analyzed for a relativistically intense partially coherent pulse, and it is found that the modulational instability is inhibited by the spectral pulse broadening. A numerical study for the one-dimensional kinetic photon equation is presented. Computer simulations reveal a Fermi-Pasta-Ulam-type recurrence phenomenon for localized broadband pulses. The results should be of importance in understanding the nonlinear propagation of broadband intense electromagnetic pulses in e-p plasmas in laser-plasma systems as well as in astrophysical plasma settings. (c) 2006 American Institute of Physics.
Abstract: We derive expressions for the coupling coefficients for electromagnetic four-wave mixing in the nonlinear quantum vacuum. An experimental setup for detection of elastic photon-photon scattering is suggested, where three incoming laser pulses collide and generate a fourth wave with a new frequency and direction of propagation. An expression for the number of scattered photons is derived and, using beam parameters for the Astra Gemini system at the Rutherford Appleton Laboratory, it is found that the signal can reach detectable levels. Problems with shot-to-shot reproducibility are reviewed, and the magnitude of the noise arising from competing scattering processes is estimated. It is found that detection of elastic photon-photon scattering may be achieved.
Abstract: A kinetic theory for radiation interacting with sound waves in an ultrarelativistic electron-positron plasma is developed. It is shown that the effect of a spatial spectral broadening of the electromagnetic pulse is to introduce a reduction of the growth rates for the decay and modulational instabilities. Such spectral broadening could be due to a finite pulse coherence length, or through the use of random phase filters, and would stabilize the propagation of electromagnetic pulses. (c) 2006 American Institute of Physics.
Abstract: In this paper we consider photon-photon scattering due to self-induced gravitational perturbations on a Minkowski background. We focus on four-wave interaction between plane waves with weakly space and time dependent amplitudes, since interaction involving a fewer number of waves is excluded by energy-momentum conservation. The Einstein-Maxwell system is solved perturbatively to third order in the field amplitudes and the coupling coefficients are found for arbitrary polarizations in the center of mass system. Comparisons with calculations based on quantum field theoretical methods are made, and the small discrepancies are explained.
Abstract: The modulational instability of broadband optical pulses in a four-state atomic system is investigated. In particular, starting from a recently derived generalized nonlinear Schrodinger equation, a wave-kinetic equation is derived. A comparison between coherent and random-phase wave states is made. It is found that the spatial spectral broadening can contribute to the nonlinear stability of ultrashort optical pulses. In practical terms, this could be achieved by using random-phase plate techniques.
Abstract: A new process associated with the nonlinear optical properties of the electromagnetic vacuum, as predicted by quantum electrodynamics, is described. This can be called photon acceleration in vacuum, and corresponds to the frequency shift that takes place when a given test photon interacts with an intense beam of background radiation. (c) 2006 Elsevier B.V. All rights reserved.
Abstract: Nonlinear interactions involving electrostatic upper-hybrid (UH), ion-cyclotron (IC), lower-hybrid (LH), and Alfven waves in quantum magnetoplasmas are considered. For this purpose, the quantum hydrodynamical equations are used to derive the governing equations for nonlinearly coupled UH, IC, LH, and Alfven waves. The equations are then Fourier analyzed to obtain nonlinear dispersion relations, which admit both decay and modulational instabilities of the UH waves at quantum scales. The growth rates of the instabilities are presented. They can be useful in applications of our work to diagnostics in laboratory and astrophysical settings. (c) 2006 American Institute of Physics.
Abstract: The effect of short wavelength quantum electrodynamic (QED) correction on plasma-wave propagation is investigated. The effect on plasma oscillations and on electromagnetic waves in an unmagnetized as well as a magnetized plasma is investigated. The effects of the short wavelength QED corrections are most evident for plasma oscillations and for extraordinary modes. In particular, the QED correction allow plasma oscillations to propagate, and the extraordinary mode loses its stop band. The significance of our results is discussed. (c) 2006 American Institute of Physics.
Abstract: We consider the modulational instability of nonlinearly interacting two-dimensional waves in deep water, which are described by a pair of two-dimensional coupled nonlinear Schrodinger equations. We derive a nonlinear dispersion relation. The latter is numerically analyzed to obtain the regions and the associated growth rates of the modulational instability. Furthermore, we follow the long term evolution of the latter by means of computer simulations of the governing nonlinear equations and demonstrate the formation of localized coherent wave envelopes. Our results should be useful for understanding the formation and nonlinear propagation characteristics of large-amplitude freak waves in deep water.
Abstract: Nonlinear oscillations within a plasma slab are analyzed. Two types of solutions are found, depending on the initial value of the electron density. The first represents regular oscillations within the plasma slab, while the second gives rise to explosive growth at the slab centre or at the edges. The results are discussed.
Abstract: The properties of amplitude modulated broadband Alfven waves are investigated. In particular, the dynamics of circularly polarized dispersive Alfven waves, governed by a derivative nonlinear Schrodinger equation, is analyzed using the Wigner formalism. The modulational instability of random phase dispersive pump Alfven waves is investigated, and it is shown that the spectral broadening gives rise to a new mode structure. (c) 2006 Elsevier B.V. All rights reserved.
Abstract: The existence of two new low-frequency electrostatic modes in quantum dusty plasmas is pointed out. These modes can be useful to diagnose charged dust impurities in micro-electro-mechanical systems.
Abstract: We present a stability analysis of a modified nonlinear Schrodinger equation describing the propagation of ultrashort pulses in negative refractive index media. Moreover, using methods of quantum statistics, we derive a kinetic equation for the pulses, making it possible to analyze and describe partial coherence in metamaterials. It is shown that a unique short pulse soliton, which is found analytically, can propagate in the medium.
Abstract: The properties of four-wave interaction via the nonlinear quantum vacuum is investigated. The effect of the quantum vacuum is to generate photons with new frequencies and wave vectors, due to elastic photon-photon scattering. An expression for the number of generated photons is derived, and using state-of-the-art laser data it is found that the number of photons can reach detectable levels. In particular, the prospect of using the high-repetition Astra Gemini system at the Rutherford Appleton Laboratory is discussed. The problem of noise sources is reviewed, and it is found that the noise level can be reduced well below the signal level. Thus, detection of elastic photon-photon scattering may for the first time be achieved.
Abstract: We consider the conversion of gravitons and photons as a four-wave mixing process. A nonlinear coupled system of equations involving two gravitons and two photons is obtained, and the energy exchange between the different degrees of freedom is found. The scattering amplitudes are obtained, from which a cross section for incoherent processes can be found. An analytical example is given, and applications to the early universe are discussed.
Abstract: In this paper we apply second-order gauge-invariant perturbation theory to investigate the possibility that the coupling between gravitational waves (GWs) and a large-scale inhomogeneous magnetic field acts as an amplification mechanism in an “almost” Friedmann-Lemaitre-Robertson-Walker Universe. The spatial inhomogeneities in the magnetic field are consistently implemented using the magnetohydrodynamic (MHD) approximation, which yields an additional source term due to the interaction of the magnetic field with velocity perturbations in the plasma. Comparing the solutions with the corresponding results in our previous work indicates that, on superhorizon scales, the interaction with the spatially inhomogeneous field in the dust regime induces the same boost as the case of a homogeneous field, at least in the ideal MHD approximation. This is attributed to the observation that the MHD induced part of the generated field effectively only contributes on scales where the coherence length of the initial field is less than the Hubble scale. At subhorizon scales, the GW induced magnetic field is completely negligible in relation to the MHD induced field. Moreover, there is no amplification found in the long-wavelength limit.
Abstract: We present an investigation of the modulational instability of partially coherent signals in electrical transmission lines. Starting from the modified Ginzburg-Landau equations and the Wigner-Moyal representation, we derive a nonlinear dispersion relation for the modulational instability. It is found that the effect of signal broadbandness reduces the growth rate of the modulational instability.
Abstract: The production of electron-positron pairs by electrostatic waves in quantum plasmas is investigated. In particular, a semiclassical governing set of equations for a self-consistent treatment of pair creation by the Schwinger mechanism in a quantum plasma is derived.
Abstract: The nonlinear propagation of incoherent magnetic field-aligned electromagnetic ion-cyclotron-Alfven (EMICA) waves in plasmas is studied. The equations governing the nonlinear interactions between incoherent EMICA waves and ion-acoustic perturbations are then used to derive a nonlinear dispersion relation, which is appropriate for investigating the modulational instability of broadband EMICA wave-packets. The case of spectral broadening of the EMICA waves is compared with the monochromatic case. It is found that the incoherency decreases the growth rate while extended regimes for the modulational instability growth rate are allowed due to the interplay between partial coherence and the dispersive effects of the EMICA waves.
Abstract: Strong-field effects in laboratory and astrophysical plasmas and high intensity laser and cavity systems are considered, related to quantum electrodynamical (QED) photon-photon scattering. Current state-of-the-art laser facilities are close to reaching energy scales at which laboratory astrophysics will become possible. In such high energy density laboratory astrophysical systems, quantum electrodynamics will play a crucial role in the dynamics of plasmas and indeed the vacuum itself. Developments such as the free-electron laser may also give a means for exploring remote violent events such as supernovae in a laboratory environment. At the same time, superconducting cavities have steadily increased their quality factors, and quantum nondemolition measurements are capable of retrieving information from systems consisting of a few photons. Thus, not only will QED effects such as elastic photon-photon scattering be important in laboratory experiments, it may also be directly measurable in cavity experiments. Here implications of collective interactions between photons and photon-plasma systems are described. An overview of strong field vacuum effects is given, as formulated through the Heisenberg-Euler Lagrangian. Based on the dispersion relation for a single test photon traveling in a slowly varying background electromagnetic field, a set of equations describing the nonlinear propagation of an electromagnetic pulse on a radiation plasma is derived. The stability of the governing equations is discussed, and it is shown using numerical methods that electromagnetic pulses may collapse and split into pulse trains, as well as be trapped in a relativistic electron hole. Effects, such as the generation of novel electromagnetic modes, introduced by QED in pair plasmas is described. Applications to laser-plasma systems and astrophysical environments are also discussed.
Abstract: We study the properties of density perturbations of a two-component plasma with a temperature difference on a homogeneous and isotropic background. For this purpose, we extend the general relativistic gauge-invariant and covariant (GIC) perturbation theory to include a multifluid with a particular equation of state (ideal gas) and imperfect fluid terms due to the relative energy flux between the two species. We derive closed sets of GIC vector and subsequently scalar evolution equations. We then investigate solutions in different regimes of interest. In particular, we study long-wavelength and arbitrary-wavelength Langmuir and ion-acoustic perturbations. The harmonic oscillations are superposed on a Jeans-type instability. We find a generalized Jeans criterion for collapse in a two-temperature plasma, which states that the species with the largest sound velocity determines the Jeans wavelength. Furthermore, we find that within the limit for gravitational collapse, initial perturbations in either the total density or charge density lead to a growth in the initial temperature difference. These results are relevant for the basic understanding of the evolution of inhomogeneities in cosmological models.
Abstract: The filamentational instability of spatially broadband femtosecond optical pulses in air is investigated by means of a kinetic wave equation for spatially incoherent photons. An explicit expression for the spatial amplification rate is derived and analyzed. It is found that the spatial spectral broadening of the pulse can lead to stabilization of the filamentation instability. Thus optical smoothing techniques could optimize current applications of ultrashort laser pulses, such as atmospheric remote sensing. (c) 2006 Optical Society of America
Abstract: A dispersion relation for electromagnetic wave propagation in a strongly magnetized cold plasma is deduced, taking photon - photon scattering into account. It is shown that the combined plasma and quantum electrodynamic effect is important for understanding the mode-structures in magnetar and pulsar atmospheres. The implications of our results are discussed.
Abstract: Using second-order gauge-invariant perturbation theory, a self-consistent framework describing the nonlinear coupling between gravitational waves and a large-scale homogeneous magnetic field is presented. It is shown how this coupling may be used to amplify seed magnetic fields to strengths needed to support the galactic dynamo. In situations where the gravitational wave background is described by an â€â€™almost” Friedmann-Lema (i) over cap tre-Robertson-Walker ( FLRW) cosmology we find that the magnitude of the original magnetic field is amplified by an amount proportional to the magnitude of the gravitational wave induced shear anisotropy and the square of the field’s initial comoving scale. We apply this mechanism to the case where the seed field and gravitational wave background are produced during inflation and find that the magnitude of the gravitational boost depends significantly on the manner in which the estimate of the shear anisotropy at the end of inflation is calculated. Assuming a seed field of 10(-34) G spanning a comoving scale of about 10 kpc today, the shear anisotropy at the end of inflation must be at least as large as 10(-40) in order to obtain a generated magnetic field of the same order of magnitude as the original seed. Moreover, contrasting the weak-field approximation to our gauge-invariant approach, we find that while both methods agree in the limit of high conductivity, their corresponding solutions are otherwise only compatible in the limit of infinitely long-wavelength gravitational waves.
Abstract: We present a statistical description of the propagation of short pulses in long optical fibers, taking into account the Kerr and nonlocal nonlinearities on an equal footing. We use the Wigner approach on the modified nonlinear Schrodinger equation to obtain a wave kinetic equation and a nonlinear dispersion relation. The latter shows that the optical pulse decoherence reduces the growth rate of the modulational instability and thereby contributes to the nonlinear stability of the pulses in long optical fibers. It is also found that the interaction between spectral broadening and nonlocality tends to extend the instability region. (c) 2005 Optical Society of America.
Abstract: The stability of colliding Bose-Einstein condensates is investigated. A set of coupled Gross-Pitaevskii equations is thus considered, and analyzed via a perturbative approach. No assumption is made on the signs ( or magnitudes) of the relevant parameters like the scattering lengths and the coupling coefficients. The formalism is therefore valid for asymmetric as well as symmetric coupled condensate wave states. A new set of explicit criteria is derived and analyzed. An extended instability region, in addition to an enhanced instability growth rate, is predicted for unstable two component bosons, as compared to the individual ( uncoupled) state.
Abstract: The nonlinear interaction, due to quantum electrodynamical effects between photons is investigated using a wave-kinetic description. Starting from a coherent wave description, we use the Wigner transform technique to obtain a set of wave-kinetic equations, the so called Wigner Moyal equations. These equations are coupled to a background radiation fluid, whose dynamics are determined by an acoustic wave equation. In the slowly varying acoustic limit, we analyse the resulting system of kinetic equations, and show that they describe instabilities, as well as Landau-like damping. The instabilities may lead to the break-up and focusing of ultra-high-intensity multi-beam systems, which in conjunction with the damping may result in stationary strong field structures. The results could be of relevance for the next generation of laser-plasma systems.
Abstract: A new nonlinear electromagnetic wave mode in a plasma is reported. Its existence depends on the interaction of an intense circularly polarized electromagnetic wave with a, plasma, where quantum electrodynamical photon-photon scattering is taken into account. As an illustration, we consider a pair plasma and.,how that the new mode can be significant in astrophysical settings and in the next generation of laser-plasma, systems.
Abstract: The nonlinear propagation of low-frequency circularly polarized waves in a magnetized dusty plasma is analyzed. It is found that wave steepening and shock formation can take place due to the presence of nonlinear quantum vacuum effects, thus giving rise to ultra-intense electromagnetic shocks. Moreover, it is shown that solitary-wave structures are admitted even under moderate astrophysical conditions. The results may have applications to astrophysical plasmas, as well as next-generation laser interactions with laboratory plasmas containing dust clusters.
Abstract: We present equations governing the interaction between incoherent light and electron-acoustic waves. The modulational instability properties of the system are studied, and the effect of partially coherent light is discussed. It is shown that partial coherence suppresses the modulational instability. However, short-wavelength modes are less affected, and will therefore dominate in, e.g., pulse filamentation. The results may be of importance to space plasmas and laser-plasma systems. (c) 2005 American Institute of Physics.
Abstract: We present a statistical description of Bose-Einstein condensates with general higher order nonlinearities. In particular, we investigate the case of cubic-quintic nonlinearities, of particular interest for dilute condensates. The implication of decoherence for the stability properties of the condensate is discussed.
Abstract: A kinetic theory for quantum Langmuir waves interacting nonlinearly with quantum ion-acoustic waves is derived. The formulation allows for a statistical analysis of the quantum correction to the Zakharov system. The influence of a background random phase on the modulational instability is given. In the coherent case, the effect of the quantum correction is to reduce the growth rate. Moreover, in the classical limit, a bifurcation develops in the dispersion curves due to the presence of partial coherence. However, the combined effect of partial coherence and a quantum correction may give rise to an increased modulational instability growth rate, as compared to the classical case. The results may be of significance in dense astrophysical plasmas and laboratory laser-plasma systems. (c) 2005 American Institute of Physics.
Abstract: A new nonlinear electromagnetic mode in a magnetized plasma is predicted. Its existence depends on the interaction of an intense, circularly polarized electromagnetic wave with a plasma, where quantum electrodynamical photon-photon scattering is taken into account. This scattering gives rise to a new coupling between the matter and the radiation. Specifically, we consider an electron-positron plasma and show that the propagation of the new mode is admitted. It could be of significance in pulsar magnetospheres, and result in energy transport between the pulsar poles.
Abstract: It is well known that a charged particle moving with constant velocity in vacuum does not radiate. In a medium, the situation can be different. If the so-called Cherenkov condition is satisfied, i.e. the particle velocity exceeds the phase speed in the medium, the particle will radiate. We show that a charge moving with a constant velocity in a gas of photons emits Cherenkov radiation, even in the gamma-ray regime, due to nonlinear quantum electrodynamical effects. Our result is evaluated with respect to the radiation background in the early universe, and it is argued that the effect can be significant.
Abstract: We present a novel nonlinear mechanism for exciting a gravitational radiation pulse (or a gravitational wave) by dust magnetohydrodynamic (DMHD) waves in dusty astrophysical plasmas. We derive the relevant equations governing the dynamics of nonlinearly coupled DMHD waves and a gravitational wave (GW). The system of equations is used to investigate the generation of a GW by compressional Alfven waves in a type II supernova. The growth rate of our nonlinear process is estimated, and the results are discussed in the context of the gravitational radiation accompanying supernova explosions. (C) 2005 Pleiades Publishing, Inc.
Abstract: The magnetohydrodynamic dynamo equation is derived within general relativity, using the covariant 1 + 3 approach, for a plasma with finite electrical conductivity. This formalism allows for a clear division and interpretation of plasma and gravitational effects, and we are not restricted to a particular space-time geometry. The results should be of interest in astrophysics and cosmology, and the formulation is well suited to gauge-invariant perturbation theory. Moreover, the dynamo equation is presented in some specific limits. In particular, we consider the interaction of gravitational waves with magnetic fields, and present results for the evolution of the linearly growing electromagnetic induction field, as well as the diffusive damping of these fields.
Abstract: We present a new dispersion relation for photons that are nonlinearly interacting with a radiation gas of arbitrary intensity due to photon-photon scattering. It is found that the photon phase velocity decreases with increasing radiation intensity, and it attains a minimum value in the limit of super-intense fields. By using Hamilton’s ray equations, a self-consistent kinetic theory for interacting photons is formulated. The interaction between an electromagnetic pulse and the radiation gas is shown to produce pulse self-compression and nonlinear saturation. Implications of our new results are discussed.
Abstract: We present exact electromagnetic solitary pulses that can be experimentally obtained within nonlinear left-handed meta-materials. The effect of pulse decoherence on the modulation instability of partially incoherent electromagnetic waves is also investigated. The results may contribute to a better understanding of nonlinear electromagnetic pulse propagation in media with negative index of refraction. (c) 2005 Elsevier B.V. All rights reserved.
Abstract: A new nonlinear electromagnetic wave mode in a magnetized dusty plasma is predicted. Its existence depends on the interaction of an intense circularly polarized electromagnetic wave with a dusty plasma, where quantum electrodynamical photon-photon scattering is taken into account. Specifically, we consider a dusty electron-positron-ion plasma and show that the propagation of the new mode is admitted. It could be of significance for the physics of supernova remnants and in neutron star formation. (C) 2005 American Institute of Physics.
Abstract: We consider radiation transport theory applied to non-dispersive but refractive media. This setting is used to discuss Minkowski’s and Abraham’s electromagnetic momentum, and to derive conservation equations independent of the choice of momentum definition. Using general relativistic kinetic theory, we derive and discuss a radiation gas energy-momentum conservation equation valid in arbitrary curved spacetime with diffractive media.
Abstract: The effects of relativistic mass increase is considered in the context of intense laser-plasma interactions. It is found that the result of the relativistic effect is to enhance the self compression and collapse of the intense laser pulse, making it possible to reach the Schwinger field limit, at which pair creation would need to be considered.
Abstract: It is shown that the collective nonlinear interactions between intense neutrino or anti-neutrino fluxes and a dense neutrino plasma are governed by a multidimensional coupled cubic Schrodinger equation in which the interaction potential is positive or negative depending on the neutrino type. The cubic Schrodinger equation describes the splitting and focusing of intense neutrino beams due to the nonlinear excitations associated with the modifications of the individual neutrino energies in a dense neutrino background.
Abstract: We show, using a covariant and gauge-invariant charged multifluid perturbation scheme, that velocity perturbations of the matter-dominated dust Friedmann-Lemaitre-Robertson-Walker model can lead to the generation of cosmic magnetic fields. Moreover, using cosmic microwave background constraints, it is argued that these fields can reach strengths of about 10(-28) G at the time the dynamo mechanism sets in, making them plausible seed field candidates.
Abstract: The derivative correction to the Heisenberg-Euler Lagrangian has been introduced. A general dispersion relation for a photon traveling on a slowly varying background electromagnetic field has been presented. A set of equations describing the nonlinear propagation of an electromagnetic pulse on a radiation fluid background is then derived. Novel modulational and filamentational instabilities are found, and using numerical methods, it has been shown that electromagnetic pulses may collapse and split into pulse trains. Also presented are analytical results concerning the collapse, split, and Mach cone formation. The implications of the results are discussed. (C) 2004 American Institute of Physics.
Abstract: Using a semiclassical approach, we analyze the collective behavior of neutrinos and antineutrinos in a dense background. Applying the Wigner transform technique, we show that the interaction can be modeled by a coupled system of nonlinear Vlasov-like equations. From these equations, we derive a dispersion relation for neutrino-antineutrino interactions on a general background. The dispersion relation admits a novel modulational instability. Moreover, we investigate the modifications of the instability due to thermal effects. The results are examined, together with a numerical example, and we discuss the induced density inhomogeneities using parameters relevant to the early Universe. (C) 2004 MAIK “Nauka / Interperiodica”.
Abstract: In quantum electrodynamics, photon-photon scattering gives rise to self-interaction terms in Maxwell’s equations. The effect will be non-zero for electromagnetic waves trapped between regions of conducting material, such as two plasma layers. It is shown numerically that this trapping in conjunction with photon-photon scattering can yield self-compression of electromagnetic waves. We discuss the relevance of our results. (C) 2004 Elsevier B.V. All rights reserved.
Abstract: Photon-photon scattering, due to photons interacting with virtual electron-positron pairs, is an intriguing deviation from classical electromagnetism predicted by quantum electrodynamics (QED). Apart from being of fundamental interest in itself, collisions between photons are believed to be of importance in the vicinity of magnetars, in the present generation intense lasers, and in intense laser-plasma/matter interactions, the latter recreating astrophysical conditions in the laboratory. We show that an intense photon pulse propagating through a radiation gas can self-focus and, under certain circumstances, collapse. This is due to the response of the radiation background, creating a potential well in which the pulse gets trapped, giving rise to photonic solitary structures. When the radiation gas intensity has reached its peak values, the gas releases part of its energy into “photon wedges,” similar to Cherenkov radiation. The results should be of importance for the present generation of intense lasers and for the understanding of localized gamma-ray bursts in astrophysical environments. They could furthermore test the predictions of QED and give means to create ultraintense photonic pulses. (C) 2004 MAIK “Nauka / Interperiodica”.
Abstract: We derive equations for nonlinearly interacting intense laser pulses and an electron-positron plasma, taking into account the combined action of the relativistic particle mass increase and the plasma density profile modification by the relativistic light ponderomotive force. The physical system is described by a modified nonlinear Schrodinger equation (NLSE). The latter predicts a modulational instability and one-dimensional light envelope solitons. In multi-dimensions, we observe the interesting phenomena of light beam focusing, light trapping in self-created density holes, and light beam filamentation. Our results should be useful in understanding the nonlinear propagation of intense laser beams in an electron-positron plasma which could be created by next generation intense lasers. (C) 2004 Elsevier B.V. All rights reserved.
Abstract: Exact nonlinear equations for magnetosonic shocklets in a uniform hot magnetoplasma are derived by using the nonlinear magnetohydrodynamic equations. Analytic, as well as numerical, solutions of the nonlinear equations are presented. Shocklike structures of the ion fluid velocity and magnetic field (or the plasma density) perturbations are obtained. The results may have relevance to the understanding of fast magnetosonic shocklets that have been recently observed by onboard instruments of the Cluster spacecraft at the Earth’s bow shock. (C) 2004 American Institute of Physics.
Abstract: Photon-photon scattering in vacuum due to the interaction with virtual electron-positron pairs is a consequence of quantum electrodynamics. A way for detecting this phenomenon has been devised based on interacting modes generated in microwave wave guides or cavities [ G. Brodin, M. Marklund, and L. Stenflo, Phys. Rev. Lett. 87, 171801 (2001) ]. Here we materialize these ideas, suggest a concrete cavity geometry, make quantitative estimates and propose experimental details. It is found that detection of photon-photon scattering can be within the reach of present day technology.
Abstract: Within the framework of the thermal wave model, an investigation is made of the longitudinal dynamics of high-energy charged-particle beams. The model includes the nonlinear self-consistent interaction between the beam and its surroundings in terms of a coupling impedance, and when resistive as well as reactive parts are included, the evolution equation becomes a generalized nonlinear Schrodinger equation including a nonlocal nonlinear term. The consequences of the resistive part on the propagation of particle bunches are examined using analytical as well as numerical methods.
Abstract: In quantum electrodynamics, photon-photon scattering can be the result of the exchange of virtual electron-positron pairs. This gives rise to a non-trivial dispersion relation for a single photon moving on a background of electromagnetic fields. Knowledge of the dispersion relation can be transferred, using standard methods, into new insights in the dynamical equations for the photons. Effectively, those equations will contain different types of self-interaction terms, depending on whether the photons are coherent or not. It is shown that coherent photons are governed by a nonlinear Schrodinger type equation, such that the self-interaction terms vanish in the limit of parallel propagating waves. For incoherent photons, a set of fluid equations can determine the evolution of the corresponding radiation gas. In the case of a self-interacting radiation fluid, it is shown that Landau damping can occur.
Abstract: We investigate the generation of electromagnetic radiation by gravitational waves interacting with a strong magnetic field in the vicinity of a vibrating Schwarzschild black hole. Such an effect may play an important role in gamma-ray bursts, supernovae, and in particular their afterglows. It may also provide an electromagnetic counterpart to gravity waves in many situations of interest, enabling easier extraction and verification of gravity wave waveforms from gravity wave detection. We set up the Einstein-Maxwell equations for the case of odd-parity gravity waves impinging on a static magnetic field as a covariant and gauge-invariant system of differential equations that can be integrated as an initial-value problem or analyzed in the frequency domain. We numerically investigate both of these cases. We find that the black hole ring-down process can produce substantial amounts of electromagnetic radiation from a dipolar magnetic field in the vicinity of the photon sphere.
Abstract: The existence of the dust acoustic wave (DAW) in a strongly magnetized electron-positron (pair)-dust plasma is demonstrated. In the DAW, the restoring force comes from the pressure of inertialess electrons and positrons, and the dust mass provides the inertia. The waves could be of interest in astrophysical settings such as the supernovae and pulsars, as well as in cluster explosions by intense laser beams in laboratory plasmas.
Abstract: The collective behaviour of neutrinos and anti neutrinos is analysed within the framework of a semi-classical model. Neutrinos close to thermal equilibrium are described by a coupled system of Schrodinger equations with nonlinear asymmetric selfinteraction potentials. The nonlinearity allows for dark soliton formation. It is shown that the interaction of incoherent neutrinos can be modelled by a coupled system of nonlinear Vlasov equations. The latter is analysed perturbatively, and a dispersion relation is derived.
Abstract: The scattering of photons off photons at the one-loop level is investigated. We give a short review of the weak field limit, as given by the first order term in the series expansion of the Heisenberg-Euler Lagrangian. The dispersion relation for a photon in a radiation gas is presented. Based on this, a wave kinetic equation and a set of fluid equations is formulated. These equations describe the interaction between a partially coherent electromagnetic pulse and an intense radiation gas. The implications of the results are discussed.
Abstract: The basic equations governing propagation of electromagnetic and gravitational waves in vacuum are nonlinear. As a consequence photon-photon interaction as well as photon-graviton interaction can take place without a medium. However, resonant interaction between less than four waves cannot occur in vacuum, unless the interaction takes place in a bounded region, such as a cavity or a waveguide. Recent results concerning resonant wave interaction in bounded vacuum regions are reviewed and extended.
Abstract: The nonlinear interaction, due to quantum electrodynamical effects, between two electromagnetic pulses and a radiation gas is investigated. It is found that the governing equations admit both modulational and filamentational instabilities. The instability growth rates are derived, and the results are discussed.
Abstract: The non-linear propagation of intense incoherent photons in a photon gas is considered. The photon-photon interactions are governed by a pair of equations comprising a wave-kinetic equation for the incoherent photons in the presence of the slowly varying energy density perturbations of sound-like waves, and an equation for the latter waves in a background where the photon coupling is caused by quantum electrodynamical effects. The coupled equations are used to derive a dispersion relation, which admits new classes of modulational instabilities of incoherent photons. The present instabilities can lead to fragmentation of broadband short photon pulses in astrophysical and laboratory settings. (C) 2004 Published by Elsevier B.V.
Abstract: We discuss how gravitational waves could amplify seed magnetic fields to strengths capable of supporting the galactic dynamo. We consider the interaction of a weak magnetic field with gravity wave distortions in almost FRW cosmologies and find that the magnitude of the original field is amplified proportionally to the wave induced shear anisotropy and, crucially, proportionally to the square of the field’s initial scale. The latter makes our mechanism particularly efficient when operating on superhorizon sized magnetic fields, like those produced during inflation. In that case, the achieved amplification can easily boost magnetic strengths, which may still lie relatively close to the galactic dynamo lower limits, well within the currently accepted range. (C) 2003 Published by Elsevier Science B.V.
Abstract: We present a proposal for a gravitational wave detector, based on the excitation of an electromagnetic mode in a resonance cavity. The mode is excited due to the interaction between a large amplitude electromagnetic mode and a quasi-monochromatic gravitational wave. The minimum metric perturbation needed for detection is estimated to be of the order 7 x 10(-23) using current data on superconducting niobium cavities. Using this value together with different standard models predicting the occurrence of merging neutron star or blackhole binaries, the corresponding detection rate is estimated to be 1-20 events per year, with a â€table top’ cavity of a few metres length.
Abstract: Recently Mendonca and Cardoso [Phys. Rev. D 66, 104009 (2002)] considered nonlinear gravitational wave packets propagating in flat space-time. They concluded that the evolution equation-to third order in amplitude-takes a similar form to what arises in nonlinear optics. Based on this equation, the authors found that nonlinear gravitational waves exhibit self-phase modulation and high harmonic generation leading to frequency up-shifting and spectral energy dilution of the gravitational wave energy. In this Brief Report we point out the fact-a possibility that seems to have been overlooked by Mendonca and Cardoso-that the nonlinear terms in the evolution equation cancels and, hence, that there is no amplitude evolution of the pulse. Finally we discuss scenarios where these nonlinearities may play a role.
Abstract: The exact 1 + 3 covariant dynamical fluid equations for a multi-component plasma, together with Maxwell’s equations are presented in such a way as to make them suitable for a gauge-invariant analysis of linear density and velocity perturbations of the Friedmann-Robertson-Walker model. In the case where the matter is described by a two-component plasma where thermal effects are neglected, a mode representing high-frequency plasma oscillations is found in addition to the standard growing and decaying gravitational instability picture. Further applications of these equations are also discussed.
Abstract: The nonlinear interaction, due to quantum electrodynamical (QED) effects between an electromagnetic pulse and a radiation background, is investigated by combining the methods of radiation hydrodynamics with the QED theory for photon-photon scattering. For the case of a single coherent electromagnetic pulse, we obtain a Zakharov-like system, where the radiation pressure of the pulse acts as a driver of acoustic waves in the photon gas. For a sufficiently intense pulse and/or background energy density, there is focusing and the subsequent collapse of the pulse. The relevance of our results for various astrophysical applications are discussed.
Abstract: In quantum electrodynamics, photon-photon scattering can be the result of the exchange of virtual electron-positron pairs. Effectively, this gives rise to self-interaction terms in Maxwell’s equations, similar to the nonlinearities due to polarization in nonlinear optics. These self-interaction terms vanish in the limit of parallel propagating waves. However if the modes generated in bounded regions are used, there will be a nonzero total effect. We show that stationary two-dimensional light bullets can form in guiding structures, due to the balancing effect of quantum electrodynamical vacuum nonlinearities on dispersion and diffraction. These light bullets are unstable and exhibit the possibility of self-focusing collapse. The consequences of our results are also discussed. (C) 2002 Elsevier Science B.V. All rights reserved.
Abstract: Self-phase modulation of spherical gravitational wave packets propagating in a flat space-time in the presence of a tenuous distribution of matter is considered. Analogies with respect to similar effects in nonlinear optics are explored. Self-phase modulation of waves emitted from a single source can eventually lead to an efficient energy dilution of the gravitational wave energy over an increasingly large spectral range. An explicit criterion for the occurrence of a significant spectral energy dilution is established.
Abstract: The effect of the Kerr nonlinearity on linear non-diffractive Bessel beams is investigated analytically and numerically using the nonlinear Schrodinger equation. The nonlinearity is shown to primarily affect the central parts of the Bessel beam, giving rise to radial compression or decompression depending on whether the nonlinearity is focusing or defocusing, respectively. The dynamical properties of Gaussian-truncated Bessel beams are also analysed in the presence of a Kerr nonlinearity. It is found that although a condition for width balance in the root-mean-square sense exists, the beam profile becomes strongly deformed during propagation and may exhibit the phenomena of global and partial collapse. (C) 2003 Elsevier Science B.V. All rights reserved.
Abstract: The nonlinear effects of amplitude jitter and ghost pulse generation, which are present in strongly dispersion-managed optical communication systems can be suppressed by alternation of the phase of the bits. A physical explanation for this effect is given that shows that with suitably chosen phase modulations the processes that give rise to the nonlinear effects will counteract each other. (C) 2002 Optical Society of America.
Abstract: In quantum electrodynamics. photon-photon scattering can be the result of the exchange of virtual electron-positron pairs. Effectively. this gives rise to self-interaction terms in Maxwell’s equations. similar to the nonlinearities due to polarisation in nonlinear optics. These self-interaction terms vanish in the limit of parallel propagating waves. However if instead the modes generated in waveguides are used, there will be a non-zero total effect. Based on this idea, we calculate the nonlinear excitation of beat wave modes and estimate the strength of this nonlinear mechanism.
Notes: International Topical Conference on Plasma Pysics, FARO, PORTUGAL, SEP 03-07, 2001
Abstract: Fermat’s principle is used to analyze the trajectories of light propagating in a radially inhomogeneous medium with a singularity in the center. It is found that the light trajectories are similar to those around a black hole, in the sense that there exists a critical radius within which the light cannot escape, but spirals into the singularity. (C) 2002 American Association of Physics Teachers.
Abstract: A statistical multistream description of quantum plasmas is formulated, using the Wigner-Poisson system as dynamical equations. A linear stability analysis of this system is carried out, and it is shown that a Landau-like damping of plane wave perturbations occurs due to the broadening of the background Wigner function that arises as a consequence of statistical variations of the wave function phase. The Landau-like damping is shown to suppress instabilities of the one- and two-stream type.
Abstract: We study the propagation of gravitational waves in a collisionless plasma with an external magnetic field parallel to the direction of propagation. Because of resonant interaction with the plasma particles the gravitational wave experiences cyclotron damping or growth, the latter case being possible if the distribution function for any of the particle species deviates from thermodynamical equilibrium. Furthermore, we examine how the damping and dispersion depends on temperature and on the ratio between the cyclotron and gravitational wave frequency. The presence of the magnetic field leads to different dispersion relations for different polarizations, which in turn imply Faraday rotation of gravitational waves.
Abstract: We consider the propagation of gravitational radiation in a magnetized multicomponent plasma. It is shown that large density perturbations can be generated, even for small deviations from flat space, provided the cyclotron frequency is much larger than the plasma frequency. Furthermore, the induced density gradients can generate frequency conversion of electromagnetic radiation, which may give rise to an indirect observational effect of the gravitational waves.
Abstract: We present a novel method for detecting nonlinearities, due to quantum electrodynamics through photon-photon scattering, in Maxwell’s equation. The photon-photon scattering gives rise to self-interaction terms which are similar to the nonlinearities due to the polarization in nonlinear optics. These self-interaction terms vanish in the limit of parallel propagating waves, but if, instead of parallel propagating waves, the modes generated in waveguides are used, there will be a nonzero total effect. Based on this idea, we calculate the nonlinear excitation of new modes and estimate the strength of this effect. Furthermore, we suggest a principal experimental setup.
Abstract: A general system of equations is derived, using the 1 + 3 orthonormal tetrad formalism, describing the influence of a plane-fronted parallel gravitational wave on a warm relativistic two-component plasma. We focus our attention on phenomena that are induced by higher order terms in the gravitational wave amplitude. In particular, it is shown that the parametric excitations of ion-acoustic waves take place due to these higher order gravitational nonlinearities. The implications of the results are discussed.
Abstract: We show that there are no new consistent cosmological perfect fluid solutions when in an open neighbourhood U of an event the fluid kinematical variables and the electric and magnetic Weyl curvature are all assumed to be rotationally symmetric about a common spatial axis, specializing the Weyl curvature tensor to algebraic Petrov type D. The consistent solutions of this kind are either locally rotationally symmetric, or are subcases of the Szekeres dust models. Parts of our results require the assumption of a barotropic equation of state. Additionally we demonstrate that local rotational symmetry of perfect fluid cosmologies follows from rotational symmetry of the Riemann curvature tensor and of its covariant derivatives only up to second order.
Abstract: It is proven that the Wahlquist perfect fluid spacetime cannot be smoothly joined to an exterior asymptotically hat vacuum region. The proof uses a power-series expansion in the angular velocity, to a precision of the second order. In this approximation, the Wahlquist metric is a special case of the rotating Whittaker spacetime. The exterior vacuum domain is treated in a like manner. We compute the conditions of matching at the possible boundary surface in both the interior and the vacuum domain. The conditions for matching the induced metrics and the extrinsic curvatures are mutually contradictory.
Abstract: We consider the dynamics of electromagnetic fields in an almost-Friedmann-Robertson-Walker universe using the covariant and gauge-invariant approach of Ellis and Bruni. Focusing on the situation where deviations from the background model are generated by tensor perturbations only, we demonstrate that the coupling between gravitational waves and a weak magnetic test field can generate electromagnetic waves. We show that this coupling leads to an initial pulse of electromagnetic waves whose width and amplitude are determined by the wavelengths of the magnetic field and gravitational waves. A number of implications for cosmology are discussed; in particular we calculate an upper bound of the magnitude of this effect using limits on the quadrupole anisotropy of the cosmic microwave background.
Abstract: We consider the interaction of a weak gravitational wave with electromagnetic fields in a thin plasma on a Minkowski background spacetime using the 1 + 3 orthonormal frame formalism. Because gravitational and electromagnetic waves satisfy the same dispersion relation, electromagnetic waves can be effectively generated as a result of this interaction. In the case of the interaction with a static magnetic field, the amplitude of the electromagnetic waves depends on the size of the excitation region in which the magnetic field is contained. It is argued that because of the presence of a plasma this process can also lead to the generation of higher harmonics of the original mode. Estimates are given for this effect in the case of a binary pulsar and a cold electron plasma. It is found that the emitted radiation will lie in the radio frequency band. We also speculate on the possible relevance of this process on situations in cosmology, in particular, whether this could be used to constrain primordial magnetic fields.
Abstract: We consider the interactions of a strong gravitational wave with electromagnetic fields using the 1+3 orthonormal tetrad formalism. A general system of equations is derived, describing the influence of a plane fronted parallel (pp) gravitational wave on a cold relativistic multicomponent plasma. We focus our attention on phenomena that are induced by terms that are higher order in the gravitational wave amplitude. In particular, it is shown that parametric excitations of plasma oscillations take place, due to higher order gravitational nonlinearities. The implications of the results are discussed.
Abstract: We consider the parametric excitation of Alfven waves by gravitational radiation propagating on a Minkowski background, parallel to an external magnetic field. As a starting point, standard ideal magnetohydrodynamics equations incorporating the curvature of space-time has been derived. The growth rate of the Alfven waves has been calculated, using the normal-mode approach. Various astrophysical applications of our investigations are discussed, and finally we demonstrate that the coupling coefficients of the interacting modes fulfill the Manley-Rowe relations.
Abstract: We consider the parametric excitation of a Langmuir wave and an electromagnetic wave by gravitational radiation, in a thin plasma on a Minkowski background. We calculate the coupling coefficients starting from a kinetic description. The growth rate of the instability is thus found. The Manley-Rowe relations are fulfilled only in the limit of a cold plasma. As a consequence, it is generally difficult to view the process quantum mechanically, i.e., as the decay of a graviton into a photon and a plasmon. Finally we discuss the relevance of our investigation to realistic physical situations and present an example. [S0031-9007(99)08933-4].
Abstract: Stationary axisymmetric perfect fluid spacetimes are investigated using the curvature description of geometries. We formulate the equations in terms of components of the Riemann tensor and the Ricci rotation coefficients in a comoving Lorentz tetrad. It is shown that the only incompressible axistationary magnetic perfect fluid is the interior Schwarzschild solution. Further, we find that all rigidly rotating axistationary fluids with magnetic Weyl tensor have local rotational symmetry. Rigidly rotating fluid spacetimes with purely electric or purely magnetic Weyl tensor are shown to be of Petrov type D.
Abstract: Locally rotationally symmetric perfect fluid solutions of Einstein’s gravitational equations are matched along the hypersurface of vanishing pressure with the NUT metric. These rigidly rotating fluids are interpreted as sources for the vacuum exterior which consists only of a stationary region of the Taub-NUT spacetime. The solution of the matching conditions leaves generally three parameters in the global solution. Examples of perfect fluid sources are discussed.
Abstract: The properties of LRS class II perfect fluid spacetimes are analysed using the description of geometries in terms of the Riemann tensor and a finite number of its covariant derivatives. In this manner it is straightforward to obtain the plane and hyperbolic analogues to the spherical symmetric case. For spherically symmetric static models the set of equations is reduced to the Tolman-Oppenheimer-Volkoff equation only. Some new non-stationary and inhomogeneous solutions with shear, expansion and acceleration of the fluid are presented. Among these are some of temporally self-similar solutions with equation of state given by p = (gamma - 1)mu, 1 < gamma < 2 and a class of solutions characterized by sigma = -1/6 Theta. We give an example of a geometry where the Riemann tensor and the Ricci rotation coefficients are not sufficient to give a complete description of the geometry. Using an extension of the method, we find the full metric in terms of curvature quantities.
Abstract: The nonlinear propagation of neutrinos and gravitons in a plasma has been considered within the framework of the general relativity. A set of governing equations for plasmas as well as for neutrinos and gravitational waves has been developed. The results should be useful for formulating the nonlinear coupling scenarios between high-energy neutrinos, intense radiation/plasmons, and gravitons, which should help to understand the combined influence of the weak nuclear, strong electromagnetic, and gravitational forces in astrophysical settings as well as in the early universe.
Abstract: The field equations for cylindrically symmetric perfect fluid models with a non-scale invariant equation of slate where the energy density is linearly related to the pressure are rewritten as a set of first order coupled ordinary differential equations. Variables are chosen such that the resulting phase space is compact and everywhere regular. The dynamical systems approach, used in the past mainly for scale invariant matter sources, is subsequently used to gain qualitative information about the space of solutions. It leads to a simple way of demonstrating the existence and properties of interior sources for cylindrically symmetric vacuum solutions. The models are shown to exhibit asymptotic scale invariance. (C) 1998 American Institute of Physics.
Abstract: We use the description of geometries in terms of the Riemann tensor and a finite number of its covariant derivatives in order to find locally rotationally symmetric (LRS) perfect-fluid solutions to Einstein’s equations. A new method is introduced, which makes it possible to choose the coordinates at any stage of the calculations. Three classes are examined, one with fluid rotation (LRS class I), one with twist in the preferred spacelike direction (LRS class Ill), and the spacetime homogeneous models. it is also shown that there are no LRS spacetimes with dependence on one null coordinate. Using an extension of the method, we find the full metric in terms of curvature quantities for LRS class I and LRS class III.
Abstract: Stationary rotating matter configurations in general relativity are considered. A formalism for general stationary space times is developed. Axisymmetric systems are discussed by the use of a nonholonomic and nonrigid frame in the three-space of the time-like Killing trajectories. Two symmetric and trace-free tensors are constructed. They characterize a class of matter states in which both the interior Schwarzschild and the Kerr solution are contained. Consistency relations for this class of perfect fluids are derived. As an example of the application of our procedure, we obtain a solution under the assumption of rigid rotation. (C) 1997 American Institute of Physics.
Abstract: The method for constructing geometries in terms of a set consisting of the curvature tensor and a finite number of its covariant derivatives is extended to determine the isometry group and to find the full line-element Comparisons are made with other tetrad methods. Two perfect fluid examples with LRS are given to illustrate the formalism: one static, conformally flat case and one stationary, rotating case with vanishing magnetic part of the Weyl tenser.
Abstract: The field equations for spacetimes with finite-dimensional Hamiltonian dynamics are discussed. Examples of models belonging to this class are the cosmological spatially homogeneous models, the astrophysically interesting static spherically symmetric models, static cylindrically symmetric models, and certain cosmological self-similar models. A number of different sources are considered. Although these models arise from quite different physical contexts, their field equations all share a common mathematical structure. This motivates a classification of Einstein’s field equations. Several classification schemes, based on properties under various variable transformations, are presented. It is shown how these schemes can be used to classify dynamical properties of the models and how one can thereby obtain qualitative information. It is also shown how one scheme can be used in order to find symmetries and exact solutions.
Abstract: We consider stimulated pair production employing strong-field QED in a high-intensity laser background. In an infinite plane wave, we show that light-cone quasi-momentum can only be transferred to the created pair as a multiple of the laser frequency, i.e. by a higher harmonic. This translates into discrete resonance conditions providing the support of the pair creation probability which becomes a delta-comb. These findings corroborate the usual interpretation of multi-photon production of pairs with an effective mass. In a pulse, the momentum transfer is continuous, leading to broadening of the resonances and sub-threshold behaviour. The peaks remain visible as long as the number of cycles per pulse exceeds unity. The resonance patterns in pulses are analogous to those of a diffraction process based on interference of the produced pairs. We finally comment on the dependence of the peak positions, and in turn the effective mass, on the pulse shape.
Abstract: We consider stimulated pair production employing strong-field QED in a high-intensity laser background. In an infinite plane wave, we show that light-cone quasi-momentum can only be transferred to the created pair as a multiple of the laser frequency, i.e. by a higher harmonic. This translates into discrete resonance conditions providing the support of the pair creation probability which becomes a delta-comb. These findings corroborate the usual interpretation of multi-photon production of pairs with an effective mass. In a pulse, the momentum transfer is continuous, leading to broadening of the resonances and sub-threshold behaviour. The peaks remain visible as long as the number of cycles per pulse exceeds unity. The resonance patterns in pulses are analogous to those of a diffraction process based on interference of the produced pairs. We finally comment on the dependence of the peak positions, and in turn the effective mass, on the pulse shape.
Abstract: A fluid model is derived, taking into account the effect of spin magnetization of electrons as well as of magnetized dust grains. The model is analyzed, and it is found that both the acoustic velocity and the Alfven velocity is decreased due to the magnetization effects. Furthermore, for low-temperature high density plasmas, it is found that the linear wave modes can be unstable, due to the magnetic attraction of individual fluid elements. The significance of our results are discussed.
Notes: 5th Interantional Conference on Physics of Dusty Plasmas, Ponta Delgada, PORTUGAL, MAY 18-23, 2008
Abstract: We consider the interaction between magnetic fields and gravity waves in almost FRW cosmologies and find that the field is amplified proportionally to its initial scale. This makes our mechanism particularly efficient when operating on super-horizon magnetic fields, like those produced during inflation. In that case, the achieved amplification can boost fields, which may still lie outside or close to the galactic dynamo lower limits, well within the accepted range.
Notes: 10th Hellenic Relativity Conference on Recent Developments in Gravity, KALLITHEA, GREECE, MAY 30-JUN 02, 2002
