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

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

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

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

Non-divergent pseudo-potential treatment of spin-polarized fermions under 1D and 3D harmonic confinement

Atom-atom scattering of bosonic one-dimensional (1D) atoms has been modeled successfully using a zero-range delta-function potential, while that of bosonic 3D atoms has been modeled successfully using Fermi-Huang's regularized s-wave pseudo-potential. Here, we derive the eigenenergies of two spin-polarized 1D fermions under external harmonic confinement interacting through a zero-range potential, which only acts on odd-parity wave functions, analytically. We also present a divergent-free zero-range potential treatment of two spin-polarized 3D fermions under harmonic confinement. Our pseudo-potential treatments are verified through numerical calculations for short-range model potentials.Comment: 9 pages, 4 figures (subm. to PRA on 03/15/2004

Fine structure of the local pseudogap and Fano effect for superconducting electrons near a zigzag graphene edge

Motivated by recent scanning tunneling experiments on zigzag-terminated graphene this paper investigates an interplay of evanescent and extended quasiparticle states in the local density of states (LDOS) near a zigzag edge using the Green's function of the Dirac equation. A model system is considered where the local electronic structure near the edge influences transport of both normal and superconducting electrons via a Fano resonance. In particular, the temperature enhancement of the critical Josephson current and 0-pi transitions are predicted.Comment: 5 pages, 5 figures, to be published in Phys. Rev.

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