Stimulated Raman backscattering of laser radiation in deep plasma channels

Stimulated Raman backscattering (RBS) of intense laser radiation confined by a single-mode plasma channel with a radial variation of plasma frequency greater than a homogeneous-plasma RBS bandwidth is characterized by a strong transverse localization of resonantly-driven electron plasma waves (EPW). The EPW localization reduces the peak growth rate of RBS and increases the amplification bandwidth. The continuum of non-bound modes of backscattered radiation shrinks the transverse field profile in a channel and increases the RBS growth rate. Solution of the initial-value problem shows that an electromagnetic pulse amplified by the RBS in the single-mode deep plasma channel has a group velocity higher than in the case of homogeneous-plasma Raman amplification. Implications to the design of an RBS pulse compressor in a plasma channel are discussed.Comment: 11 pages, 3 figures; submitted to Physics of Plasma

Strongly coupled large-angle stimulated Raman scattering of short laser pulses in plasma-filled capillaries

Strongly coupled large-angle stimulated Raman scattering (LA SRS) of a short intense laser pulse proceeds in a plane plasma-filled capillary differently than in a plasma with open boundaries. Oblique mirror reflections off capillary walls partly suppress the lateral convection of scattered radiation and increase the growth rate of the instability: the convective gain of the LA SRS falls with an angle much slower than in an unbounded plasma and even for the near-forward SRS can be close to that of the direct backscatter. The long-term evolution of LA SRS in the interior of the capillary is dominated by quasi-one-dimensional leaky modes, whose damping is related to the transmission of electromagnetic waves through capillary walls.Comment: 11 pages, 6 figures; to be submitted to Physics of Plasma

Estimation of the particle-antiparticle correlation effect for pion production in heavy ion collisions

Estimation of the back-to-back pi-pi correlations arising due to evolution of the pionic field in the course of pion production process is given for central heavy nucleus collisions at moderate energies.Comment: 6 LaTeX pages + 5 ps figure

Radiative double electron capture by bare nucleus with emission of one photon

Calculation of the cross-section for the process of double electron capture by bare nucleus with emission of a single photon is presented. The double electron capture is evaluated within the framework of Quantum Electrodynamics (QED). Line-Profile Approach (LPA) is employed. Since the radiative double electron capture is governed by the electron correlation, corrections to the interelectron interaction were calculated with high accuracy, partly to all orders of the perturbation theory

Nonlinear evolution of the plasma beatwave: Compressing the laser beatnotes via electromagnetic cascading

The near-resonant beatwave excitation of an electron plasma wave (EPW) can be employed for generating the trains of few-femtosecond electromagnetic (EM) pulses in rarefied plasmas. The EPW produces a co-moving index grating that induces a laser phase modulation at the difference frequency. The bandwidth of the phase-modulated laser is proportional to the product of the plasma length, laser wavelength, and amplitude of the electron density perturbation. The laser spectrum is composed of a cascade of red and blue sidebands shifted by integer multiples of the beat frequency. When the beat frequency is lower than the electron plasma frequency, the red-shifted spectral components are advanced in time with respect to the blue-shifted ones near the center of each laser beatnote. The group velocity dispersion of plasma compresses so chirped beatnotes to a few-laser-cycle duration thus creating a train of sharp EM spikes with the beat periodicity. Depending on the plasma and laser parameters, chirping and compression can be implemented either concurrently in the same, or sequentially in different plasmas. Evolution of the laser beatwave end electron density perturbations is described in time and one spatial dimension in a weakly relativistic approximation. Using the compression effect, we demonstrate that the relativistic bi-stability regime of the EPW excitation [G. Shvets, Phys. Rev. Lett. 93, 195004 (2004)] can be achieved with the initially sub-threshold beatwave pulse.Comment: 13 pages, 11 figures, submitted to Physical Review

A quantum hydrodynamics approach to the formation of new types of waves in polarized two-dimension systems of charged and neutral particles

In this paper we explicate a method of quantum hydrodynamics (QHD) for the study of the quantum evolution of a system of polarized particles. Though we focused primarily on the two-dimension physical systems, the method is valid for three-dimension and one-dimension systems too. The presented method is based upon the Schr\"{o}dinger equation. Fundamental QHD equations for charged and neutral particles were derived from the many-particle microscopic Schr\"{o}dinger equation. The fact that particles possess the electric dipole moment (EDM) was taken into account. The explicated QHD approach was used to study dispersion characteristics of various physical systems. We analyzed dispersion of waves in a two-dimension (2D) ion and hole gas placed into an external electric field which is orthogonal to the gas plane. Elementary excitations in a system of neutral polarized particles were studied for 1D, 2D and 3D cases. The polarization dynamics in systems of both neutral and charged particles is shown to cause formation of a new type of waves as well as changes in the dispersion characteristics of already known waves. We also analyzed wave dispersion in 2D exciton systems, in 2D electron-ion plasma and 2D electron-hole plasma. Generation of waves in 3D system neutral particles with EDM by means of the beam of electrons and neutral polarized particles is investigated.Comment: 15 pages, 7 figure

Two-photon correlations as a sign of sharp transition in quark-gluon plasma

The photon production arising due to time variation of the medium has been considered. The Hamilton formalism for photons in time-variable medium (plasma) has been developed with application to inclusive photon production. The results have been used for calculation of the photon production in the course of transition from quark-gluon phase to hadronic phase in relativistic heavy ion collisions. The relative strength of the effect as well as specific two- photon correlations have been evaluated. It has been demonstrated that the opposite side two-photon correlations are indicative of the sharp transition from the quark-gluon phase to hadrons.Comment: 23 pages, 2 figure

Observability of a projected new state of matter: a metallic superfluid

Dissipationless quantum states, such as superconductivity and superfluidity, have attracted interest for almost a century. A variety of systems exhibit these macroscopic quantum phenomena, ranging from superconducting electrons in metals to superfluid liquids, atomic vapours, and even large nuclei. It was recently suggested that liquid metallic hydrogen could form two new unusual dissipationless quantum states, namely the metallic superfluid and the superconducting superfluid. Liquid metallic hydrogen is projected to occur only at an extremely high pressure of about 400 GPa, while pressures on hydrogen of 320 GPa having already been reported. The issue to be adressed is if this state could be experimentally observable in principle. We propose four experimental probes for detecting it.Comment: in print in Phys. Rev. Let