Giant acceleration in slow-fast space-periodic Hamiltonian systems

Motion of an ensemble of particles in a space-periodic potential well with a weak wave-like perturbation imposed is considered. We found that slow oscillations of wavenumber of the perturbation lead to occurrence of directed particle current. This current is amplifying with time due to giant acceleration of some particles. It is shown that giant acceleration is linked with the existence of resonant channels in phase space

The Ground State of the ``Frozen'' Electron Phase in Two-Dimensional Narrow-Band Conductors with a Long-Range Interelectron Repulsion. Stripe Formation and Effective Lowering of Dimension

In narrow-band conductors a weakly screened Coulomb interelectron repulsion can supress narrow-band electrons' hopping, resulting in formation of a ``frozen'' electron phase which differs principally from any known macroscopic self-localized electron state including the Wigner crystal. In a zero-bandwidth limit the ``frozen'' electron phase is a classical lattice system with a long-range interparticle repulsion. The ground state of such systems has been considered in the case of two dimensions for an isotropic pair potential of the mutual particle repulsion. It has been shown that particle ordering into stripes and effective lowering of dimension universally resides in the ground state for any physically reasonable pair potential and for any geometry of the conductor lattice. On the basis of this fact a rigorous general procedure to fully describe the ground state has been formulated. Arguments have been adduced that charge ordering in High-T_c superconductors testifies to presence of a ``frozen'' electron phase in these systems.Comment: 5 pages, LaTeX 2.09, 1 figure in external PostScript files. To appear in Phys.Rev B Rapid Communication

Common proper motion companions to nearby stars : ages and evolution

A set of 41 nearby stars (closer than 25 pc) is investigated which have very wide binary and common proper motion (CPM) companions at projected separations between 1000 and 200,000 AU. These companions are identified by astro-metric positions and propermotions from the NOMAD catalog. Based mainly on measures of chromospheric and X-ray activity, age estimation is obtained for most of 85 identified companions. Color-absolute magnitude diagrams are constructed to test whether CPM companions are physically related to the primary nearby stars and have the same age. Our carefully selected sample includes three remote white dwarf companions to main-sequence stars and two systems (55 Cnc and GJ 777A) of multiple planets and distant stellar companions. Ten new CPM companions, including three of extreme separations, are found. Multiple hierarchical systems are abundant; more than 25% of CPM components are spectroscopic or astrometric binaries or multiples themselves. Two new astrometric binaries are discovered among nearby CPM companions, GJ 264 and HIP 59000, and preliminary orbital solutions are presented. The Hyades kinematic group (or stream) is presented broadly in the sample, but we find few possible thick-disk objects and no halo stars. It follows from our investigation that moderately young (age ≾ to Gyr) thin-disk dwarfs are the dominating species in the near CPM systems, in general agreement with the premises of the dynamical survival paradigm

Nonlinear surface magneto-plasmonics in Kretschmann multilayers

The nonlinear magneto-plasmonics aims to utilize plasmonic excitations to control the mechanisms and taylor the efficiencies of the non-linear light frequency conversion at the nanoscale. We investigate the mechanisms of magnetic second harmonic generation in hybrid gold-cobalt-silver multilayer structures, which support propagating surface plasmon polaritons at both fundamental and second harmonic frequencies. Using magneto-optical spectroscopy in Kretschmann geometry, we show that the huge magneto-optical modulation of the second harmonic intensity is dominated by the excitation of surface plasmon polaritons at the second harmonic frequency, as shown by tuning the optical wavelength over the spectral region of strong plasmonic dispersion. Our proof-of-principle experiment highlights bright prospects of nonlinear magneto-plasmonics and contributes to the general understanding of the nonlinear optics of magnetic surfaces and interfaces.Comment: Main Manuscript: 5 pages, 3 figures. Supplementary Information: 10 pages, 7 figure

Muons with E_th >= 1 Gev and Mass Composition in the Energy Range 10^{18}-10^{20} ev Observed by Yakutsk Eas Array

The ratio of the muon flux density to charged particle flux density at distances of 300 and 600 m from the shower axis (\rhom(300)/\rhos(300) and \rhom(600)/\rhos(600)) is measured. In addition, the energy dependence of \rhom(1000) is analysed for showers with energies above $10^{18}$ eV. A comparison between the experimental data and calculations performed with the QGSJET model is given for the cases of primary proton, iron nucleus and gamma- ray. We conclude that the showers with \E\ge3\times10^{18} eV can be formed by light nuclei with a pronounced fraction of protons and helium nuclei. It is not excluded however that a small part of showers with energies above $10^{19}$ eV could be initiated by primary gamma-rays.Comment: 19th European Cosmic Ray Symposium, Aug 30 - Sep 3 2004, Florence, Italy. 3 pages, 1 figure. Submitted for publication in International Journal of Modern Physics