Showing papers on "Relativistic plasma published in 2016"
TL;DR: In this article, the electric and chiral current densities in inhomogeneous relativistic plasma were derived using the chiral kinetic theory, and they were analyzed in the regimes with and without a drift of the plasma.
Abstract: Using the chiral kinetic theory we derive the electric and chiral current densities in inhomogeneous relativistic plasma. We also derive equations for the electric and chiral charge chemical potentials that close the Maxwell equations in such a plasma. The analysis is done in the regimes with and without a drift of the plasma as a whole. In addition to the currents present in the homogeneous plasma (Hall current, chiral magnetic, chiral separation, and chiral electric separation effects, as well as Ohm's current) we derive several new terms associated with inhomogeneities of the plasma. Apart from various diffusion-like terms, we find also new dissipation-less terms that are independent of relaxation time. Their origin can be traced to the Berry curvature modifications of the kinetic theory.
65 citations
TL;DR: In this article, the authors make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions.
Abstract: Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focus on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The "flares" are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model.more » Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. As a result, higher magnetization studies are promising and will be carried out in the future.« less
63 citations
TL;DR: It is demonstrated experimentally and numerically via 3D particle-in-cell simulations that the degree of ellipticity of the laser polarization strongly influences the spatial-intensity distribution of the beam of multi-MeV protons.
Abstract: Control of the collective response of plasma particles to intense laser light is intrinsic to relativistic optics, the development of compact laser-driven particle and radiation sources, as well as investigations of some laboratory astrophysics phenomena. We recently demonstrated that a relativistic plasma aperture produced in an ultra-thin foil at the focus of intense laser radiation can induce diffraction, enabling polarization-based control of the collective motion of plasma electrons. Here we show that under these conditions the electron dynamics are mapped into the beam of protons accelerated via strong charge-separation-induced electrostatic fields. It is demonstrated experimentally and numerically via 3D particle-in-cell simulations that the degree of ellipticity of the laser polarization strongly influences the spatial-intensity distribution of the beam of multi-MeV protons. The influence on both sheath-accelerated and radiation pressure-accelerated protons is investigated. This approach opens up a potential new route to control laser-driven ion sources.
63 citations
TL;DR: In this article, an electron beam is generated with a spatial structure that can be changed by varying the characteristics of the laser pulse, resulting in a relativistic plasma aperture and diffraction.
Abstract: Shining intense laser light onto a thin aluminium foil creates a relativistic plasma aperture—and diffraction. As a result, an electron beam is generated with a spatial structure that can be changed by varying the characteristics of the laser pulse.
55 citations
TL;DR: In this article, a head-on collision between two dust ion acoustic solitary waves (DIASWs) travelling in the opposite direction in a weakly relativistic plasma composed of four distinct particle populations, namely, superthermal electrons, positrons, and immobile dust, is investigated.
Abstract: A head-on collision between two dust ion acoustic solitary waves (DIASWs) travelling in the opposite direction in a weakly relativistic plasma composed of four distinct particle populations, namely, weakly relativistic ion fluid, superthermal electrons as well as positrons, and immobile dust, is investigated. By employing extended Poincare-Lighthill-Kuo method, two Korteweg-de Vries (KdV) equations are derived. The analytical phase shift after a head-on collision of two dust ion acoustic (DIA) solitary waves is also obtained. The combined effects of relativistic factor (β), electron to positron temperature ratio (α), ion to electron temperature ratio (σ), positron to electron density ratio (P), dust density ratio (d), and superthermality of electrons as well as positrons (via κ) on the phase shifts are numerically studied. All these physical parameters have also changed the potential amplitude and the width of colliding solitary waves. It is found that the presence of superthermal electrons as well as positrons and dust grains has emphatic influence on the phase shifts and potential pulse profiles of compressive DIA solitons. Our results are general and may be helpful in understanding a head-on collision between two DIASWs in astrophysical and laboratory plasmas, especially the interaction of pulsar relativistic winds with supernova ejecta that produces the superthermal particles and relativistic ions.
49 citations
TL;DR: This scheme opens a practical and promising route to generate bright attosecond XUV pulses with desirable ellipticities in a straightforward and efficient way for a number of applications.
Abstract: Ultrafast extreme ultra-violet sources are widely used to study material properties but the polarization control necessary for certain applications has proven difficult. Here, the authors propose a scheme to generate circularly or highly elliptically polarized XUV pulses using a relativistic plasma mirror.
44 citations
TL;DR: In this paper, the authors make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reaction.
Abstract: Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short time scales. These are likely due to rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reaction. We focus on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The "flares" are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of radiation reaction, and some astrophysical applications of this model. Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from Crab Nebula. Higher magnetization studies are promising and will be carried out in the future.
32 citations
TL;DR: In this paper, the Korteweg-de Vries Burgers (KdVB)-like equation is derived to study the characteristics of nonlinear propagation of ion acoustic solitions in a highly relativistic plasma containing relativists ions and nonextensive distribution of electrons and positrons using the well known reductive perturbation technique.
Abstract: The Korteweg-de Vries Burgers (KdVB)-like equation is derived to study the characteristics of nonlinear propagation of ion acoustic solitions in a highly relativistic plasma containing relativistic ions and nonextensive distribution of electrons and positrons using the well known reductive perturbation technique. The KdVB-like equation is solved employing the Bernoulli's equation method taking unperturbed positron to electron concentration ratio, electron to positron temperature ratio, strength of nonextensivity, ion kinematic viscosity, and highly relativistic streaming factor. It is found that these parameters significantly modify the structures of the solitonic excitation. The ion acoustic shock profiles are observed due to the influence of ion kinematic viscosity. In the absence of dissipative term to the KdVB equation, compressive and rarefactive solitons are observed in case of superthermality, but only compressive solitons are found for the case of subthermality.
31 citations
TL;DR: The efficiency limit of relativistic high-order-harmonic emission from solid targets achievable with tailored light fields is considered and the maximum energy conversion efficiency is shown to reach as high as 10% for the harmonics in the range of 80-200 eV.
Abstract: We consider the efficiency limit of relativistic high-order-harmonic emission from solid targets achievable with tailored light fields. Using one-dimensional particle-in-cell simulations, the maximum energy conversion efficiency is shown to reach as high as 10% for the harmonics in the range of 80--200 eV and is largely independent of laser intensity and plasma density. The waveforms most effective at driving harmonics have a broad spectrum with a lower-frequency limit set by the width of the incident pulse envelope and an upper limit set by the relativistic plasma frequency.
30 citations
TL;DR: In this paper, the authors discuss the technical approach to the conceptually new 100 TW, 100 fs, λ = 9-11 μm CO2 laser BESTIA (Brookhaven Experimental Supra-Terawatt Infrared at ATF) that encompasses several innovations applied for the first time to molecular gas lasers.
Abstract: Expanding the scope of relativistic plasma research to wavelengths longer than the λ/≈ 0.8–1.1 μm range covered by conventional mode-locked solid-state lasers would offer attractive opportunities due to the quadratic scaling of the ponderomotive electron energy and critical plasma density with λ. Answering this quest, a next-generation mid-IR laser project is being advanced at the BNL ATF as a part of the user facility upgrade. We discuss the technical approach to this conceptually new 100 TW, 100 fs, λ = 9–11 μm CO2 laser BESTIA (Brookhaven Experimental Supra-Terawatt Infrared at ATF) that encompasses several innovations applied for the first time to molecular gas lasers. BESTIA will enable new regimes of laser plasma accelerators. One example is shock-wave ion acceleration (SWA) from gas jets. We review ongoing efforts to achieve stable, monoenergetic proton acceleration by dynamically shaping the plasma density profile from a hydrogen gas target with laser-produced blast waves. At its full power, 100 TW BESTIA promises to achieve proton beams at an energy exceeding 200 MeV. In addition to ion acceleration in over-critical plasma, the ultra-intense mid-IR BESTIA will open up new opportunities in driving wakefields in tenuous plasmas, expanding the landscape of laser wakefield accelerator (LWFA) studies into the unexplored long-wavelength spectral domain. Simple wavelength scaling suggests that a 100 TW CO2 laser beam will be capable of efficiently generating plasma 'bubbles' a thousand times greater in volume compared with a near-IR solid state laser of an equivalent power. Combined with a femtosecond electron linac available at the ATF, this wavelength scaling will facilitate the study of external seeding and staging of LWFAs.
14 citations
TL;DR: These findings establish a new class of bright laboratory sources of electromagnetic radiation, being applicable to travelling waves of any nature, that provides a novel framework for creating new emitters and for interpreting observations in many fields of science.
Abstract: In various media the elementary components can emit traveling waves such as electromagnetic, gravitational or acoustic types. If these elementary emitters are synchronized, the resulting emission is coherent. Moreover, the faster the emitters approach an observer, the more intense and directional their apparent emission is, with associated frequency increase. Multi-stream flows ubiquitously occur in media (such as with shock waves and jets in astrophysical and laboratory plasmas) and produce fast moving density singularities, where high concentration and synchronism can bring constructive interference. However, a singularity emitting such characteristic coherent radiation has not been demonstrated yet. We show this general phenomenon in laser-driven relativistic plasma, which is an ideal medium for realizing these effects in the laboratory under controllable conditions. Our experiments and simulations reveal bright coherent soft x-ray radiation from nanoscale electron density singularities in multi-stream plasma. They constitute a new compact x-ray source of ultrashort duration, demanded in numerous applications. In general, singularities can be bright sources of other types of traveling waves. Thus our findings open new opportunities in different fields of science. For example, gravitational wave generation, as proposed in ultrahigh-energy accelerators, can be significantly enhanced by intentionally induced density singularities in the particle bunches. Further, we anticipate that multi-stream flows in cosmic media can produce intense bursts of coherent electromagnetic and/or gravitational waves, especially at longer wavelengths which facilitate constructive interference. We can then expect to observe more directional short wavelength bursts from cosmic emitters approaching at relativistic speeds. Thus, we present a new framework for interpreting a broad range of experimental results.
TL;DR: In this article, the authors consider the re-acceleration model in which a weak shock of M s ≈ 1.2 -1.5 sweeps through the intracluster plasma with a preshock population of relativistic electrons.
Abstract: The Toothbrush radio relic associated with the merging cluster 1RXS J060303.3 is presumed to be produced by relativistic electrons accelerated at merger-driven shocks. Since the shock Mach number inferred from the observed radio spectral index, M radio ≈ 2.8, is larger than that estimated from X-ray observations, M X ≲ 1.5, we consider the re-acceleration model in which a weak shock of M s ≈ 1.2 - 1.5 sweeps through the intracluster plasma with a preshock population of relativistic electrons. We nd the models with a power-law momentum spectrum with the slope, s ≈ 4.6, and the cutoff Lorentz factor,γ e,c ≈ 7-8 x 10 4 can reproduce reasonably well the observed proles of radio uxes and integrated radio spectrum of the head portion of the Toothbrush relic. This study conrms the strong connection between the ubiquitous presence of fossil relativistic plasma originated from AGNs and the shock-acceleration model of radio relics in the intracluster medium.
TL;DR: In this paper, fast magnetic field annihilation in a collisionless plasma is induced by using TEM(1,0) laser pulse and the magnetic quadrupole structure formation, expansion and annihilation stages are demonstrated with 2.5D particle-in-cell simulations.
Abstract: Fast magnetic field annihilation in a collisionless plasma is induced by using TEM(1,0) laser pulse. The magnetic quadrupole structure formation, expansion and annihilation stages are demonstrated with 2.5-dimensional particle-in-cell simulations. The magnetic field energy is converted to the electric field and accelerate the particles inside the annihilation plane. A bunch of high energy electrons moving backwards is detected in the current sheet. The strong displacement current is the dominant contribution which induces the longitudinal inductive electric field.
TL;DR: In this article, the effects of Coulomb elctron-ion collisions and plasma density gradient on the Weibel instability in inertial confinement fusion are investigated, and the results are indicative that the corrected collision of Weibel stability growth rate of the relativistic region near the corona, near the core, increases with an increasing relativity parameter.
Abstract: In this paper, the effects of Coulomb elctron-ion collisions and plasma density gradient, $$\eta$$
, on the Weibel instability in inertial confinement fusion are investigated. The results are indicative that the corrected collision of Weibel instability growth rate of the relativistic region near the corona, $$\eta >0.3$$
, increases with increasing relativistic parameter, $$\upgamma$$
. Also, near the fuel core as $$\eta$$
goes down, the corrected collisional growth rate decreases with increasing $$\upgamma$$
for $$\mathrm{{\upgamma }}<6$$
and and increases with increasing $$\upgamma$$
for $$\upgamma >6$$
. Therefore, for $$\upgamma <6$$
, the effect of collision and fuel density gradient tend to stabilize the Weibel instability in fuel core, with the Weibel growth rate below the collisionless value. Also deposition condition of relativistic electron beam energy can be shifted to the fuel core for the suitable ignition.
TL;DR: In this article, the optical properties of PMs at the incident laser frequency when irradiated directly at relativistic intensity (1e18 < I_0 < 1e19 W/cm^2) by near-normally incident (4 degree), high contrast, 30 fs, 800 nm laser pulses were investigated.
Abstract: We report an experimental-computational study of the optical properties of plasma mirrors (PMs) at the incident laser frequency when irradiated directly at relativistic intensity (1e18 < I_0 < 1e19 W/cm^2) by near-normally incident (4 degree), high-contrast, 30 fs, 800 nm laser pulses. We find that such relativistic PMs are highly reflective (0.6 to 0.8), and focus a significant fraction of reflected light to intensity as large as 10I_0 at distance f as small 25 microns from the PM, provided that pre-pulses do not exceed 1e14 W/cm^2 prior to 20 ps before arrival of the main pulse peak. Particle-in-cell simulations show that focusing results from denting of the reflecting surface by light pressure combined with relativistic transparency, and that reflectivity and f can be adjusted by controlling pre-plasma length L over the range 0.5 < L < 3 microns. Pump-probe reflectivity measurements show the PM's focusing properties evolve on a ps time scale.
TL;DR: In this study, the Lorentz boosted frame technique was applied to the problem of warm wave-breaking limits of plasma waves with relativistic phase velocity and the dynamics for the Vlasov equation in different LorentZ frames were found to be independent of γ_{p}.
Abstract: For certain classes of relativistic plasma problems, performing numerical calculations in a Lorentz boosted frame can be even more advantageous for gridded momentum-space-time (e.g., Vlasov) problems than has been demonstrated for position space-time problems and result in a potential reduction in the number of calculations needed by a factor ∼γ 6b . In this study, the Lorentz boosted frame technique was applied to the problem of warm wave-breaking limits of plasma waves with relativistic phase velocity. The numerical results are consistent with analytic conclusions. By appropriate normalization and for sufficiently warm plasma, the dynamics for the Vlasov equation in different Lorentz frames were found to be independent of γp.
TL;DR: In this article, the authors investigated the effect of relativistic electrons on compressive and rarefactive solons in the model of a dusty plasma and found that the flux of negative charges from the dust particles, together with the effects of the relatvistic electrons, appears to balance the positive charges of Cairns distributed ions for nearly constant growth of amplitudes.
Abstract: In this model of a dusty plasma, we have investigated dust acoustic waves consisting of electrons with weak relativistic effects, Cairns distributed cold ions and negatively charged mobile dust. Dust acoustic (DA) compressive and rarefactive solitons of various amplitudes are established. The parameter is solely due to the rest energy and not due to kinetic energy in this relativistic plasma. This is one of the most significant results of our investigation. Also, the flux of negative charges from the dust particles, together with the effect of the relativistic electrons, appears to balance the positive charges of Cairns distributed ions for nearly constant growth of amplitudes.
TL;DR: In this paper, the authors derived the three dimensional nonlinear Zakharov-Kuznetsov equation and also presented its solution for the fast and slow ion acoustic wave in a weakly relativistic magnetorotating plasma in the presence of non-Maxwellian electrons and warm ions.
Abstract: Linear and nonlinear electrostaticion acoustic waves in a weakly relativistic magnetorotating plasma in the presence of non-Maxwellian electrons and warm ions have been examined. The system under consideration has yielded two solutions, namely, the fast and slow acoustic modes which have been observed to depend on the streaming velocity, ion to electron temperature ratio, and the nonthermality parameter of the non-Maxwellian electrons. Using the multiple time scale analysis, we have derived the three dimensional nonlinear Zakharov–Kuznetsov equation and also presented its solution. Both compressive and rarefactive solitary structures have been found in consonance with the satellite observations. It has been observed that although the linear dispersion relation gives both fast and slow ion acoustic waves, the solitary structures form only for the fast acoustic mode. The dependence of the characteristics of the solitary structures on several plasma parameters has also been explored. The present investigation may be beneficial to understanding the rotating plasma environments such as those found in the planetary magnetospheres of Saturn and Jupiter.
TL;DR: In this paper, a short account of the current status of the field, with particular emphasis on the theoretical challenges connected to the observed ultra-fast variability events and to the emission of flat spectrum radio quasars in the very high energy band.
Abstract: Blazars are high-energy engines providing us natural laboratories to study particle acceleration, relativistic plasma processes, magnetic field dynamics, black hole physics. Key informations are provided by observations at high-energy (in particular by Fermi/LAT) and very-high energy (by Cherenkov telescopes). I give a short account of the current status of the field, with particular emphasis on the theoretical challenges connected to the observed ultra-fast variability events and to the emission of flat spectrum radio quasars in the very high energy band.
TL;DR: In this article, the authors reviewed the physical processes in a plasma under the action of relativistically strong electromagnetic waves generated by high-power lasers and focused on nonlinear waves in a laser plasma for the creation of compact electron accelerators.
Abstract: Physical processes in a plasma under the action of relativistically strong electromagnetic waves generated by high-power lasers have been briefly reviewed. These processes are of interest in view of the development of new methods for acceleration of charged particles, creation of sources of bright hard electromagnetic radiation, and investigation of macroscopic quantum-electrodynamical processes. Attention is focused on nonlinear waves in a laser plasma for the creation of compact electron accelerators. The acceleration of plasma bunches by the radiation pressure of light is the most efficient regime of ion acceleration. Coherent hard electromagnetic radiation in the relativistic plasma is generated in the form of higher harmonics and/or electromagnetic pulses, which are compressed and intensified after reflection from relativistic mirrors created by nonlinear waves. In the limit of extremely strong electromagnetic waves, radiation friction, which accompanies the conversion of radiation from the optical range to the gamma range, fundamentally changes the behavior of the plasma. This process is accompanied by the production of electron–positron pairs, which is described within quantum electrodynamics theory.
TL;DR: In this article, field aligned whistler mode waves are analyzed in the presence of DC field in background plasma having relativistic distribution function in the magnetosphere of Uranus, and the results can be used for comparative study of planetary magnetospheres.
28 Oct 2016
TL;DR: In this paper, the authors explored the injection of helium electrons at the helium-lithium interface of a lithium heat pipe oven and the subsequent acceleration in the beam-produced plasma wake.
Abstract: Localized injection of electrons within a relativistic plasma wake can potentially produce an ultrashort, monoenergetic electron bunch Recent experiments at the FACET facility at SLAC explored the injection of helium electrons at the helium-lithium interface of a lithium heat pipe oven and the subsequent acceleration in the beam-produced plasma wake Electrons accelerated to over 10 GeV in 30 cm of plasma were observed as a distinct charge bunch
TL;DR: In this paper, a hydrodynamic formalism is developed to describe collisional, anisotropic instabilities in a relativistic plasma, that are usually described with kinetic theory tools.
Abstract: We develop a purely hydrodynamic formalism to describe collisional, anisotropic instabilities in a relativistic plasma, that are usually described with kinetic theory tools. Our main motivation is the fact that coarse-grained models of high particle number systems give more clear and comprehensive physical descriptions of those systems than purely kinetic approaches, and can be more easily tested experimentally as well as numerically. In particular, we aim at developing a theory that describes both a background non-equilibrium fluid configurations and its perturbations, to be able to account for the backreaction of the latter on the former. Our system of equations includes the usual conservation laws for the energy-momentum tensor and for the electric current, and the equations for two new tensors that encode the information about dissipation. To make contact with kinetic theory, we write the different tensors as the moments of a non-equilibrium one-particle distribution function (1pdf) which, for illustrative purposes, we take in the form of a Grad-like ansatz. Although this choice limits the applicability of the formalism to states not far from equilibrium, it retains the main features of the underlying kinetic theory. We assume the validity of the Vlasov-Boltzmann equation, with a collision integral given by the Anderson-Witting prescription, which is more suitable for highly relativistic systems than Marle's (or Bhatnagar, Gross and Krook) form, and derive the conservation laws by taking its corresponding moments. We apply our developments to study the emergence of instabilities in an anisotropic, but axially symmetric background. For small departures of isotropy we find the dispersion relation for normal modes, which admit unstable solutions for a wide range of values of the parameter space.
TL;DR: A self-consistent transport theory for a relativistic plasma is developed and semianalytical forms of the electrical resistivity, thermoelectric, and thermal conductivity tensors for a Lorentzian plasma in a magnetic field are provided.
Abstract: In this work, a self-consistent transport theory for a relativistic plasma is developed. Using the notation of Braginskii [S. I. Braginskii, in Reviews of Plasma Physics, edited by M. A. Leontovich (Consultants Bureau, New York, 1965), Vol. 1, p. 174], we provide semianalytical forms of the electrical resistivity, thermoelectric, and thermal conductivity tensors for a Lorentzian plasma in a magnetic field. This treatment is then generalized to plasmas with arbitrary atomic number by numerically solving the linearized Boltzmann equation. The corresponding transport coefficients are fitted by rational functions in order to make them suitable for use in radiation-hydrodynamic simulations and transport calculations. Within the confines of linear transport theory and on the assumption that the plasma is optically thin, our results are valid for temperatures up to a few MeV. By contrast, classical transport theory begins to incur significant errors above k_{B}T∼10 keV, e.g., the parallel thermal conductivity is suppressed by 15% at k_{B}T=20 keV due to relativistic effects.
CERN1
TL;DR: In this paper, it was shown that the quasiadiabatic mode cannot be a substitute for the conventional adiabatic paradigm so that, ultimately, the present findings seem to exclude the possibility of a successful accelerated dynamics solely based on relativistic viscous fluids.
Abstract: The viscous inhomogeneities of a relativistic plasma determine a further class of entropic modes whose amplitude must be sufficiently small since curvature perturbations are observed to be predominantly adiabatic and Gaussian over large scales. When the viscous coefficients only depend on the energy density of the fluid the corresponding curvature fluctuations are shown to be almost adiabatic. After addressing the problem in a gauge-invariant perturbative expansion, the same analysis is repeated at a non-perturbative level by investigating the nonlinear curvature inhomogeneities induced by the spatial variation of the viscous coefficients. It is demonstrated that the quasiadiabatic modes are suppressed in comparison with a bona fide adiabatic solution. Because of its anomalously large tensor to scalar ratio the quasiadiabatic mode cannot be a substitute for the conventional adiabatic paradigm so that, ultimately, the present findings seems to exclude the possibility of a successful accelerated dynamics solely based on relativistic viscous fluids. If the dominant adiabatic mode is not affected by the viscosity of the background a sufficiently small fraction of entropic fluctuations of viscous origin cannot be a priori ruled out.
TL;DR: In this article, the dynamics of relativistic laser-produced plasma expansion across a transverse magnetic field is investigated based on a one dimensional two-fluid model that includes pressure, enthalpy, and rest mass energy, and the expansion is studied in the limit of λ D ǫ ≤ R L (Larmor radius) for magnetized electrons and ions.
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TL;DR: In this paper, the authors showed that the dielectric constant, magnetic reluctivity, Debye length and the plasma frequency depend on temperature in the early universe and found the favorable conditions for the relativistic plasma from this calculations.
Abstract: Renormalization scheme of QED (Quantum Electrodynamics) at high temperatures is used to calculate the effective parameters of relativistic plasma in the early universe. Renormalization constants of QED play role of effective parameters of the theory and can be used to determine the collective behavior of the medium. We explicitly show that the dielectric constant, magnetic reluctivity, Debye length and the plasma frequency depend on temperature in the early universe. Propagation speed, refractive index, plasma frequency and Debye shielding length of a QED plasma are computed at extremely high temperatures in the early universe. We also found the favorable conditions for the relativistic plasma from this calculations.
TL;DR: In this article, a variational extension of the variational principle with the modified test function for the Spitzer function with momentum conservation in the electron-electron collision is investigated in uniformly magnetized plasma.
Abstract: A fully relativistic extension of the variational principle with the modified test function for the Spitzer function with momentum conservation in the electron–electron collision is investigated in uniformly magnetized plasma. The term of the momentum conserving constraint in Hirshman's variational calculation is studied. The model developed is extended for arbitrary temperatures and covers exactly the asymptotic for when , and the results obtained are suited to facilitate the development of a rigorous variational formulation of current drive efficiency in tokamak plasma.
22 May 2016
TL;DR: In this article, the J-KAREN-P laser was used to generate high-order harmonics by relativistic -irradiance multi-terawatt femtosecond laser focused onto gas jet targets.
Abstract: We discuss the new regime of high-order harmonic generation by relativistic -irradiance multi-terawatt femtosecond lasers focused onto gas jet targets [PRL, 108, 135004, 2012; NJP, 16, 093003, 2014]. The laser induces multi-stream relativistic plasma flow resulting in the formation of density singularities: structurally stable, oscillating electron spikes coherently emitting high-frequency radiation. Here we analyse the dependence of the harmonic yield on the focal spot quality and derive the required laser parameters for efficient harmonics generation. We show the status of the J-KAREN-P laser [IEEE J. Sel. Topics Quantum Electron., 21, 1601118, 2015] and report on the progress towards satisfying these requirements.