Self-consistent current sheets and filaments in relativistic collisionless plasma with arbitrary energy distribution of particles.

A new class of self-consistent planar current sheets and cylindrical current filaments with a functional freedom for the resultant spatial profiles is found analytically for collisionless plasma. Invariants of particle motion are employed to obtain exact stationary solutions of Vlasov-Maxwell equations for arbitrary energy distribution of particles. This method automatically takes into account complicated particle motion in a self-consistent magnetic field, can be equally well applied to relativistic and nonrelativistic plasma, and yields a much wider class of solutions as compared to models of the Harris-Bennett type and their known generalizations. We discuss typical analytical solutions and general properties of magnetostatic neutral structures: spatial scales, magnitudes of current and magnetic field, degree of anisotropy of particle distributions, and possible equipartition of magnetic and particle energies.

Cooperative recombination of a quantized high-density electron-hole plasma in semiconductor quantum wells.

We investigate photoluminescence from a high-density electron-hole plasma in semiconductor quantum wells created via intense femtosecond excitation in a strong perpendicular magnetic field, a fully quantized and tunable system. At a critical magnetic field strength and excitation fluence, we observe a clear transition in the band-edge photoluminescence from omnidirectional output to a randomly directed but highly collimated beam. In addition, changes in the linewidth, carrier density, and magnetic field scaling of the photoluminescence spectral features correlate precisely with the onset of random directionality, indicative of cooperative recombination from a high-density population of free carriers in a semiconductor environment.

Nonlinear dynamics of gravity and matter creation in a cosmology with an unbounded Hamiltonian.

Nonlinear dynamics and stability properties of a cosmological model of spatially homogeneous coupled gravity and matter fields is analyzed using methods of classical mechanics. The system exhibits regions of chaos and dramatic changes in structural stability as the strength of the coupling between the fields is varied. Numerical simulations suggest that Hamiltonian systems with structure appropriate for describing matter-gravity interaction constitute a new class of nonlinear systems with very unusual and rich dynamics.