17,160 research outputs found

    Exact Expressions for Minor Hysteresis Loops in the Random Field Ising Model on a Bethe Lattice at Zero Temperature

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    We obtain exact expressions for the minor hysteresis loops in the ferromagnetic random field Ising model on a Bethe lattice at zero temperature in the case when the driving field is cycled infinitely slowly.Comment: Replaced with the published versio

    Spinodal decomposition: An alternate mechanism of phase conversion

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    The scenario of homogeneous nucleation is investigated for a first order quark-hadron phase transition in a rapidly expanding background of quark gluon plasma. It is found that significant supercooling is possible before hadronization begins. This study also suggests that spinodal decomposition competes with nucleation and may provide an alternative mechanism for phase conversion.Comment: LaTeX, 4 pages with 3 Postscript figures. Talk given at International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP 2001), Nov. 26-30, 2001, Jaipur, Indi

    Linear and nonlinear properties of Rao-dust-Alfv\'en waves in magnetized plasmas

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    The linear and nonlinear properties of the Rao-dust-magnetohydrodynamic (R-D-MHD) waves in a dusty magnetoplasma are studied. By employing the inertialess electron equation of motion, inertial ion equation of motion, Amp\`ere's law, Faraday's law, and the continuity equation in a plasma with immobile charged dust grains, the linear and nonlinear propagation of two-dimensional R-D-MHD waves are investigated. In the linear regime, the existence of immobile dust grains produces the Rao cutoff frequency, which is proportional to the dust charge density and the ion gyrofrequency. On the other hand, the dynamics of an amplitude modulated R-D-MHD waves is governed by the cubic nonlinear Schroedinger equation. The latter has been derived by using the reductive perturbation technique and the two-timescale analysis which accounts for the harmonic generation nonlinearity in plasmas. The stability of the modulated wave envelope against non-resonant perturbations is studied. Finally, the possibility of localized envelope excitations is discussed.Comment: 30 pages, 8 figures, to appear in Physics of Plasma

    Nonlinear wave-wave interactions in quantum plasmas

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    Wave-wave interaction in plasmas is a topic of important research since the 16th century. The formation of Langmuir solitons through the coupling of high-frequency (hf) Langmuir and low-frequency (lf) ion-acoustic waves, is one of the most interesting features in the context of turbulence in modern plasma physics. Moreover, quantum plasmas, which are ubiquitous in ultrasmall electronic devices, micromechanical systems as well as in dense astrophysical environments are a topic of current research. In the light of notable interests in such quantum plasmas, we present here a theoretical investigation on the nonlinear interaction of quantum Langmuir waves (QLWs) and quantum ion-acoustic waves (QIAWs), which are governed by the one-dimensional quantum Zakharov equations (QZEs). It is shown that a transition to spatiotemporal chaos (STC) occurs when the length scale of excitation of linear modes is larger than that of the most unstable ones. Such length scale is, however, to be larger (compared to the classical one) in presence of the quantum tunneling effect. The latter induces strong QIAW emission leading to the occurrence of collision and fusion among the patterns at an earlier time than the classical case. Moreover, numerical simulation of the QZEs reveals that many solitary patterns can be excited and saturated through the modulational instability (MI) of unstable harmonic modes. In a longer time, these solitons are seen to appear in the state of STC due to strong QIAW emission as well as by the collision and fusion in stochastic motion. The energy in the system is thus strongly redistributed, which may switch on the onset of Langmuir turbulence in quantum plasmas.Comment: 6 pages, 6 figures (To appear in AIP Conf. Proceedings 2010

    Self-Diffusion in 2D Dusty Plasma Liquids: Numerical Simulation Results

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    We perform Brownian dynamics simulations for studying the self-diffusion in two-dimensional (2D) dusty plasma liquids, in terms of both mean-square displacement and velocity autocorrelation function (VAF). Super-diffusion of charged dust particles has been observed to be most significant at infinitely small damping rate γ\gamma for intermediate coupling strength, where the long-time asymptotic behavior of VAF is found to be the product of t1t^{-1} and exp(γt)\exp{(-\gamma t)}. The former represents the prediction of early theories in 2D simple liquids and the latter the VAF of a free Brownian particle. This leads to a smooth transition from super-diffusion to normal diffusion, and then to sub-diffusion with an increase of the damping rate. These results well explain the seemingly contradictory scattered in recent classical molecular dynamics simulations and experiments of dusty plasmas.Comment: 10 pages 5 figures, accepted by PR

    Rossby rogons in atmosphere and in the solar photosphere

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    The generation of Rossby rogue waves (Rossby rogons), as well as the excitation of bright and dark Rossby envelpe solitons are demonstrated on the basis of the modulational instability (MI) of a coherent Rossby wave packet. The evolution of an amplitude modulated Rossby wave packet is governed by one-dimensional (1D) nonlinear Schr\"odinger equation (NLSE). The latter is used to study the amplitude modulation of Rossby wave packets for fluids in Earth's atmosphere and in the solar photosphere. It is found that an ampitude modulated Rossby wave packet becomes stable (unstable) against quasi-stationary, long wavelength (in comparision with the Rossby wave length) perturbations, when the carrier Rossby wave number satisfies k2<1/2k^2 < 1/2 or 2+13\sqrt{2}+13 or 1/2<k2<2+11/2<k^2<\sqrt{2}+1). It is also shown that a Rossby rogon or a bright Rossby envelope soliton may be excited in the shallow water approximation for the Rossby waves in solar photosphere. However, the excitation of small or large scale perturbations may be possible for magnetized plasmas in the ionosphereic EE-layer.Comment: 6 pages, 5 figures; To appear in Europhysics Letter