P-wave diffusion in fluid-saturated medium

This paper considers the propagating P-waves in the fluid-saturated mediums that are categorized to fall into two distinct groups: insoluble and soluble mediums. P-waves are introduced with slowness in accordance to Snell Law and are shown to relate to the medium displacement and wave diffusion. Consequently, the results bear out that the propagating P-waves in the soluble medium share similar diffusive characteristic as of insoluble medium. Nonetheless, our study on fluid density in the mediums show that high density fluid promotes diffusive characteristic whiles low density fluid endorses non-diffusive P-wav

Geometric phases in 2D and 3D polarized fields: geometrical, dynamical, and topological aspects

Geometric phases are a universal concept that underpins numerous phenomena involving multi-component wave fields. These polarization-dependent phases are inherent in interference effects, spin-orbit interaction phenomena, and topological properties of vector wave fields. Geometric phases have been thoroughly studied in two-component fields, such as two-level quantum systems or paraxial optical waves. However, their description for fields with three or more components, such as generic nonparaxial optical fields routinely used in modern nano-optics, constitutes a nontrivial problem. Here we describe geometric, dynamical, and total phases calculated along a closed spatial contour in a multi-component complex field, with particular emphasis on 2D (paraxial) and 3D (nonparaxial) optical fields. We present several equivalent approaches: (i) an algebraic formalism, universal for any multi-component field; (ii) a dynamical approach using the Coriolis coupling between the spin angular momentum and reference-frame rotations; and (iii) a geometric representation, which unifies the Pancharatnam-Berry phase for the 2D polarization on the Poincar\'e sphere and the Majorana-sphere representation for the 3D polarized fields. Most importantly, we reveal close connections between geometric phases, angular-momentum properties of the field, and topological properties of polarization singularities in 2D and 3D fields, such as C-points and polarization M\"obius strips.Comment: 21 pages, 11 figures, to appear in Rep. Prog. Phy

Inhomogeneous CuO_{6} Tilt Distribution and Charge/Spin Correlations in La_{2-x-y}Nd_{y}Sr_{x}CuO$_{4} around commensurate hole concentration

Phononic and magnetic Raman scattering are studied in La$_{2-x-y}$Nd$_{y}$Sr$_{x}$CuO$_{4}$ with three doping concentrations: x ~ 1/8, y = 0; x ~ 1/8, y = 0.4; and x = 0.01, y = 0. We observe strong disorder in the tilt pattern of the CuO_{6} octahedra in both the orthorhombic and tetragonal phases which persist down to 10 K and are coupled to bond disorder in the cation layers around 1/8 doping independent of Nd concentration. The weak magnitude of existing charge/spin modulations in the Nd doped structure does not allow us to detect the specific Raman signatures on lattice dynamics or two-magnon scattering around 2200 cm-1.Comment: to be published in Phys. Rev.

Global Energetics of Thirty-Eight Large Solar Eruptive Events

We have evaluated the energetics of 38 solar eruptive events observed by a variety of spacecraft instruments between February 2002 and December 2006, as accurately as the observations allow. The measured energetic components include: (1) the radiated energy in the GOES 1 - 8 A band; (2) the total energy radiated from the soft X-ray (SXR) emitting plasma; (3) the peak energy in the SXR-emitting plasma; (4) the bolometric radiated energy over the full duration of the event; (5) the energy in flare-accelerated electrons above 20 keV and in flare-accelerated ions above 1 MeV; (6) the kinetic and potential energies of the coronal mass ejection (CME); (7) the energy in solar energetic particles (SEPs) observed in interplanetary space; and (8) the amount of free (nonpotential) magnetic energy estimated to be available in the pertinent active region. Major conclusions include: (1) the energy radiated by the SXR-emitting plasma exceeds, by about half an order of magnitude, the peak energy content of the thermal plasma that produces this radiation; (2) the energy content in flare-accelerated electrons and ions is sufficient to supply the bolometric energy radiated across all wavelengths throughout the event; (3) the energy contents of flare-accelerated electrons and ions are comparable; (4) the energy in SEPs is typically a few percent of the CME kinetic energy (measured in the rest frame of the solar wind); and (5) the available magnetic energy is sufficient to power the CME, the flare-accelerated particles, and the hot thermal plasma

Transition from Free to Interacting Composite Fermions away from ν\nu=1/3

Spin excitations from a partially populated composite fermion level are studied above and below $\nu=1/3$. In the range $2/7<\nu<2/5$ the experiments uncover significant departures from the non-interacting composite fermion picture that demonstrate the increasing impact of interactions as quasiparticle Landau levels are filled. The observed onset of a transition from free to interacting composite fermions could be linked to condensation into the higher order states suggested by transport experiments and numerical evaluations performed in the same filling factor range.Comment: 4 pages, 5 figures, to appear in PR

Spin texture and magnetoroton excitations at nu=1/3

Neutral spin texture (ST) excitations at nu=1/3 are directly observed for the first time by resonant inelastic light scattering. They are determined to involve two simultaneous spin flips. At low magnetic fields, the ST energy is below that of the magnetoroton minimum. With increasing in-plane magnetic field these mode energies cross at a critical ratio of the Zeeman and Coulomb energies of eta(c)=0.020 +/- 0.001. Surprisingly, the intensity of the ST mode grows with temperature in the range in which the magnetoroton modes collapse. The temperature dependence is interpreted in terms of a competition between coexisting phases supporting different excitations. We consider the role of the ST excitations in activated transport at nu=1/3

Topological Properties of Spatial Coherence Function

Topology of the spatial coherence function is considered in details. The phase singularity (coherence vortices) structures of coherence function are classified by Hopf index and Brouwer degree in topology. The coherence flux quantization and the linking of the closed coherence vortices are also studied from the topological properties of the spatial coherence function.Comment: 9 page

Growth rate of YBCO single grains containing Y-2411(M)

Y-Ba-Cu-O (YBCO) single grains have the potential to generate large trapped magnetic fields for a variety of engineering applications, and research on the processing and properties of this material has attracted world-wide interest. In particular, the introduction of flux pinning centres to the large grain microstructure to improve its current density, Jc, and hence trapped field, has been investigated extensively over the past decade. Y 2Ba4CuMOx [Y-2411(M)], where M = Nb, Ta, Mo, W, Ru, Zr, Bi and Ag, has been reported to form particularly effective flux pinning centres in YBCO due primarily to its ability to exist as nano-size inclusions in the superconducting phase matrix. However, the addition of the Y-2411(M) phase to the precursor composition complicates the melt-processing of single grains. We report an investigation of the growth rate of single YBCO grains containing Y-2411(Bi) phase inclusions and Y2O3. The superconducting properties of these large single grains have been measured specifically to investigate the effect of Y2O3 on broadening the growth window of these materials

A Collision of Subclusters in Abell 754

We present direct evidence of a collision of subclusters in the galaxy cluster Abell 754. Our comparison of new optical data and archival ROSAT PSPC X-ray data reveal three collision signatures predicted by n-body/hydrodynamical simulations of hierarchical cluster evolution. First, there is strong evidence of a non-hydrostatic process; neither of the two major clumps in the galaxy distribution lies on the off-center peak of the X-ray emission from the intracluster gas. Second, the peak of the X-ray emission is elongated perpendicular to the collision axis defined by the centroids of the two galaxy clumps. Third, there is evidence of compression-heated gas; one of A754's two X-ray temperature components (Henry & Briel 1995) is among the hottest observed in any cluster and hotter than that inferred from the velocity dispersion of the associated galaxy clump. These signatures are consistent with the qualitative features of simulations (Evrard 1990a,b) in which two subclusters have collided in the plane of the sky during roughly the last Gyr. The detection of such collisions is crucial for understanding both the dynamics of individual clusters and the underlying cosmology. First, for systems like A754, estimating the cluster X-ray mass from assumptions of hydrostatic equilibrium and isothermality is incorrect and may produce the discrepancies sometimes found between X-ray masses and those derived from gravitational lens models (Babul & Miralda-Escude 1994). Second, the fraction of nearby clusters in which subclusters have collided in the last Gyr is especially sensitive to the mean mass density parameter Omega_0 (cf. Richstone et al. 1992; Evrard et al. 1993; Lacey & Cole 1993). With a large, well-defined cluster sample, it will be possible to place a new and powerful constraint on cosmological models.Comment: 4 pages + 1 color figure (Postscript). Accepted for Publication in ApJ Letter