Photon dispersion in a strong magnetic field

In an external magnetic field analytical properties are studied of the photon polarization tensor calculated as the electron-positron loop in the Furry picture. The polarization tensor is reexpressed as a sum over singular contributions coming from e⁺e^?-pair photocreation in semidiscrete Landau states. The solutions of the photon dispersion equation (i.e., the one for the poles of the photon propagator) are described. The shape of the photon dispersion curve obtained is responsible for the effect of photon deflection by a strong magnetic field. No physically reliable solutions, apart from spurions, are found for the longitudinal photon mode. An infinite number of solutions with complex space-momentum are found, with no apparnet ghosts among them. An attempt is made to interprete the former in terms of possible bound and quasibound states of electron and positron pairs.     

Photon splitting in an ultrastrong magnetic field

We analyze the splitting of a photon with energy ω below the e ⁺ e ⁻ pair-production threshold in an ultrastrong magnetic field. We use the amplitudes found by employing the operator diagrammatic technique. In a field considerably above the critical values the process amplitudes become independent of the field strength. A study of the polarization operator of a photon in an external field of arbitrary strength in the energy range considered in the present investigation shows that there is only one set of polarizations of the initial and final photons for which the splitting amplitude is nonzero. Zh. éksp. Teor. Fiz. 111, 52–62 (January 1997)     

Neutrino propagation in a medium with a magnetic field

Data on the mean multiplicity of strange hadrons produced in minimum bias proton-proton and central nucleus-nucleus collisions at momenta between 2.8 and 400 GeV/c per nucleon have been compiled. The multiplicities for nucleon-nucleon interactions were constructed. The ratios of strange particle multiplicity to participant nucleon as well as to pion multiplicity are larger for central nucleus-nucleus collisions than for nucleon-nucleon interactions at all studied energies. The data at AGS energies suggest that the latter ratio saturates with increasing masses of the colliding nuclei. The strangeness to pion multiplicity ratio observed in nucleon-nucleon interactions increases with collision energy in the whole energy range studied. A qualitatively different behaviour is observed for central nucleus-nucleus collisions: the ratio rapidly increases when going from Dubna to AGS energies and changes little between AGS and SPS energies. This change in the behaviour can be related to the increase in the entropy production observed in central nucleus-nucleus collisions at the same energy range. The results are interpreted within a statistical approach. They are consistent with the hypothesis that the Quark Gluon Plasma is created at SPS energies, the critical collision energy being between AGS and SPS energies.     

Photon and axion splitting in an inhomogeneous magnetic field

The axion–photon system in an external magnetic field, when the direction of propagation of axions and photons is orthogonal to the direction of the external magnetic field, displays a continuous axion–photon duality symmetry in the limit the axion mass is neglected. The conservation law that follow in this effective (2+1)$(2+1)$-dimensional theory from this symmetry is obtained. The magnetic field interaction is seen to be equivalent to first order to the interaction of a complex charged field with an external electric potential, where this fictitious “electric potential” is proportional to the external magnetic field. This allows one to solve for the scattering amplitudes using already known scalar QED results. From the scalar QED analog the axion and the photon are symmetric and antisymmetric combinations of particle and antiparticle. If one considers therefore scattering experiments in which the two spatial dimensions of the effective theory are involved nontrivially, one observes that both particle and antiparticle components of photons and axions are preferentially scattered in different directions, thus producing the splitting or decomposition of the photon and axion into their particle and antiparticle components in an inhomogeneous magnetic field. This observable in principle effect is of first order in the axion–photon coupling, unlike the “light shining through a wall phenomena”, which is second order.     

Ultrashort pulse propagation in carbon nanotubes in a magnetic field

The problem of ultra-short optical pulse behavior in a system of carbon nanotubes with an applied magnetic field parallel to the nanotube axis was considered. The electromagnetic field was explored using the Maxwell equations. The electronic system of the carbon nanotubes was a quantum system and was mechanically investigated for the case of low temperatures. The distributional pattern of the ultra short pulses and their collision were established by means of numerical modeling.     

Wave propagation in quasi-one-dimensional quantum plasma in a magnetic field

A cold electron gas fills the lowest Landau level for high enough magnetic fields and for low enough densities. Such a situation is expected to occur for the Malmberg-O'Neil experiment and also for pulsar crusts and atmospheres. Such plasmas behave as a quasi-one-dimensional system and exhibit some peculiarities in their wave structure. We study the dispersion and damping of the low frequencies, i.e., the whistler mode, and the extraordinary mode for zero temperature. The behavior of the whistler mode depends critically on the filling number _Fc=_F/ , where _F is the Fermi energy and is the cyclotron frequency. The one-dimensional character of the system affects the pair excitation spectrum and thus the decay of modes. We find that, in contrast to the three-dimensional situation, the plasma mode and the extraordinary mode remain undamped, while the whistler mode is undamped for all but very highk values.     

Photon damping caused by electron-positron pair production in a strong magnetic field

Damping of an electromagnetic wave in a strong magnetic field is analyzed in the kinematic region near the threshold of electron-positron pair production. Damping of the electromagnetic field is shown to be noticeably nonexponential in this region. The resulting width of the photon γ→e ⁺ e ^? decay is considerably smaller than previously known results.     

Photon echoes generated by reversing magnetic field gradients in a rubidium vapor

We propose a photon echo quantum memory scheme using detuned Raman coupling to long-lived ground states. In contrast to previous three-level schemes based on controlled reversible inhomogeneous broadening that use sequences of pi pulses, the scheme does not require accurate control of the coupling dynamics to the ground states. We present a proof-of-principle experimental realization of our proposal using rubidium atoms in a warm vapor cell. The Raman resonance line is broadened using a magnetic field that varies linearly along the direction of light propagation. Inverting the magnetic field gradient rephases the atomic dipoles and re-emits the light pulse in the forward direction.     

Photon propagation in torsion background

The existence of a torsion background in spacetime at cosmological scales can be tested from the timing of high-energy photons from AGN. The observations of anomalous photon dispersion from Markarian 501 by Magic gamma ray telescope can be explained by the presence of torsion background and it puts limits on the torsion background at κ S ₀ < 10⁻¹⁸ GeV⁻¹.     

Magnetic field driven domain-wall propagation in magnetic nanowires

The mechanism of magnetic field induced magnetic domain-wall (DW) propagation in a nanowire is revealed: A static DW cannot exist in a homogeneous magnetic nanowire when an external magnetic field is applied. Thus, a DW must vary with time under a static magnetic field. A moving DW must dissipate energy due to the Gilbert damping. As a result, the wire has to release its Zeeman energy through the DW propagation along the field direction. The DW propagation speed is proportional to the energy dissipation rate that is determined by the DW structure. The negative differential mobility in the intermediate field is due to the transition from high energy dissipation at low field to low energy dissipation at high field. For the field larger than the so-called Walker breakdown field, DW plane precesses around the wire, leading to the propagation speed oscillation.     

Photon emission by electrons and positrons created in a strong slowly rotating magnetic field

We study the electrodynamic process in which a photon is emitted together with an e ^--e ⁺ pair in the presence of a strong slowly rotating magnetic field. In particular, the spectrum of photons produced in this way is calculated starting from an effective Lagrangian that allows at tree level for the process itself. The magnetic field strengths we have in mind are in such a way that, although our model is an oversimplified version of the real physical situation, the results can be applied only in some particular astrophysical scenarios (magnetars, massive black holes).Received: 15 January 2004, Revised: 19 April 2004, Published online: 23 June 2004     

Wave propagation in strongly coupled quasi-one-dimensional quantum plasma in a magnetic field

A cold electron gas fills the lowest Landau level for superstrong magnetic fields and very low densities. In such cases, in general, the potential energy of the particles is equal to or greater than their kinetic energy (strongly coupled plasmas), and a special approach is called for. The STLS (Singwi, Tosi, Land, and Sjolander) approximation scheme is used to study the dispersion and damping of the low-frequency modes, i.e., the whistler and the extraordinary modes for zero temperature. The lowest order dispersion for all modes in consideration are unaffected by correlations, but for undamped plasmas the correlation term is of the ordera ² c ^–2. Further,( ²) for the whistler mode becomes infinite at=3; its behavior critically depends on the filling number _Fc = _F/, where _F is the Fermi energy and is the electron cyclotron frequency.     

Magnetostatic wave propagation in a double-layered film structure under inclined magnetic field

Under inclined magnetic field, the propagation characteristics of magnetostatic waves (MSWs) for a double-layered waveguided structure are theoretically studied by using surface permeability method. A new concept called ‘mode interlamination coupling’ is proposed by analysis of mode spectrum, which develops a generalized understanding of the MSWs propagating in a layered structure. A similar treatment can be applied to the situation of multi-layered structure under inclined field. In addition, the dispersion relation and delay characteristics of coupled mode in two different YIG films are studied by numerical analogue at inclination angle from 5 to 20°. The results indicate that the MSWs propagating in double-layer structure is appropriate for high frequency range (8.4∼10 GHz) under inclined field, and it has an optimum range of delay rate superior to single film by adjusting the inclination angle of the magnetic field. Apparently, the performances of double-layered film structure under inclined field have potential dominance in channelization and stability of signal processing for the application of magneto-optic waveguided devices in the future.     

Hydrogen-like atom in a superstrong magnetic field: Photon emission and relativistic energy level shift

Following our previous work, additional arguments are presented that in superstrong magnetic fields B ? (Zα)² B ₀, B ₀ = m ² c ³/e? ≈ 4.41 × 10¹³ G, the Dirac equation and the Schrödinger equation for an electron in the nucleus field following from it become spatially one-dimensional with the only z coordinate along the magnetic field, “Dirac” spinors become two-component, while the 2 × 2 matrices operate in the {0; 3} subspace. Based on the obtained solution of the Dirac equation and the known solution of the “onedimensional” Schrödinger equation by ordinary QED methods extrapolated to the {0; 3} subspace, the probability of photon emission by a “one-dimensional” hydrogen-like atom is calculated, which, for example, for the Lyman-alpha line differs almost twice from the probability in the “three-dimensional” case. Similarly, despite the coincidence of nonrelativistic energy levels, the calculated relativistic corrections of the order of (Zα)⁴ substantially differ from corrections in the absence of a magnetic field. A conclusion is made that, by analyzing the hydrogen emission spectrum and emission spectra at all, we can judge in principle about the presence or absence of superstrong magnetic fields in the vicinity of magnetars (neutron stars and probably brown dwarfs). Possible prospects of applying the proposed method for calculations of multielectron atoms are pointed out and the possibility of a more reliable determination of the presence of superstrong magnetic fields in magnetars by this method is considered.     

Effective field theory approach to light propagation in an external magnetic field

The recent PVLAS experiment observed rotation of polarization and ellipticity when a linearly polarized laser beam passes through a transverse magnetic field. The phenomenon cannot be explained in conventional QED. We attempt to accommodate the result by employing an effective theory for the electromagnetic field alone. No new particles with a mass of order the laser frequency or below are assumed. To quartic terms in the field strength, a parity-violating term appears besides the two ordinary terms. The rotation of polarization and ellipticity are computed for parity-asymmetric and -symmetric experimental set-ups. While rotation occurs in an ideal asymmetric case and has the same magnitude as ellipticity, it disappears in a symmetric set-up like PVLAS. This would mean that we have to appeal to some low-mass new particles with nontrivial interactions with photons to understand the PVLAS result. PACS 12.20.-m; 12.20.Fv; 42.25.Lc; 42.25.Ja     

Sound propagation in two-dimensional electron systems in strong magnetic field

Under the dHvA condition, the sound velocity in two-dimensional electron systems is expected to oscillate strongly as a function of 1/γ₀ which is the ratio of the ideal Fermi energy to the field energy.     

���޴ų��м��������������Ĵ��������о�

分析了有限磁场中激光等离子体通道周围为有耗气体介质时激光引导电磁脉冲传播的一般模式的传播特性,建立了有限磁场中激光等离子体通道引导电磁脉冲的几何模型,导出了广义柱坐标系下各向异性介质中纵向场所满足的波动方程及纵向场与横向场的关系。利用边界条件给出了有限磁场中激光引导电磁脉冲传播模式的严格特征方程,重点讨论了传播常数随等离子体参数、周围介质参数和外加磁场的变化。结果表明,有限磁场中激光引导电磁脉冲的传播特性比无磁场或外加无穷大磁场时更具有可控性。