Terms Of Anisotropy Parameter Research Articles

Effect of anisotropy on the field-induced quantum critical properties of the three-dimensionals=12Heisenberg model

The field induced quantum critical properties of the three dimensional spin-1/2 anisotropic antiferromagnetic Heisenberg model has been studied. We have investigated the quantum phase transition between the spiral order and field induced ferromagnetic order by means of Bose-Einstein condensation of magnons in terms of a bosonic representation. The effect of in-plane anisotropy on the critical properties has been studied via the bosonic model by Green's function approach. We have found an analytic expression for the gap exponent in addition to numerical results for the critical magnetic field in terms of anisotropy parameter. The in-plane anisotropy breaks the U(1) symmetry explicitly which changes the universal behavior by a drastic change on the gap exponent. Moreover, the critical magnetic field depends strongly on the in-plane anisotropies. The divergence of the transverse structure factor at the antiferromagnetic wave vector confirms the onset of the magnetic order which scales with the negative value of gap exponent as the magnetic field approaches the critical one. The transverse staggered magnetization as an order parameter vanishes with exponent $\beta=0.5$ when the magnetic field reaches its critical value in low field region.

Elliptic flow, Kasner universe and holographic dual of RHIC fireball

We consider a holographic dual of hydrodynamics of N=4 SYM plasma that undergoes non-isotropic three-dimensional expansion relevant to RHIC fireball. Our model is a natural extension of the Bjorken's one-dimensional expansion, and it describes an elliptic flow whose v2 and eccentricity are given in terms of anisotropy parameters. Holographic renormalization shows that absence of conformal anomaly in the SYM theory constrains our local rest frame to be a Kasner spacetime. We show that the Kasner spcetime provides a simple description of the anisotropically expanding fluid within a well-controled approximation. We also find that the dual geometry determines some of the hydrodynamic quantities in terms of the initial condition and the fundamental constants.

The rupture process of theMJ=7.2 1995 Hyogo-ken Nanbu (Kobe) earthquake deduced fromS-wave polarization analysis

SUMMARY The use of S-wave polarization analysis for constraining high-frequency (>1 Hz) source parameters of large earthquake has been previously illustrated by Bouin & Bernard (1994) and Guatteri & Cocco (1996). In this paper, we show the efficiency of such a methodology applied to a data set in the presence of strong non-linear and liquefaction effects for the particular case of the 1995 Hyogo-ken Nanbu (Kobe) earthquake. The 11 strong-motion recordings from the closest stations to the fault plane have been analysed in the 0.6–2.0 Hz frequency band. We first correct the recorded ground motion data for the effect of shallow crustal anisotropy in the Kobe area, which allows us to remove part of the complexity of the observed S-wave polarigrams. Our results in terms of anisotropy parameters are in good agreement with those of previous studies performed in the same area. They show evidence, far from the faults, of a fast S-wave polarization oriented nearly parallel to the regional compressive stress direction, and, close to the faults, of a fast S-wave polarization oriented parallel to the faults' strikes. The corrected S-wave polarigrams are then interpreted in terms of rupture propagation along an extended fault. We consider three different faulting mechanisms: a pure right-lateral mechanism and two mechanisms with 30 and 50 per cent reverse components. The polarization data and the triggering times at the selected stations allow the identification of a set of subsources, demonstrating the need for a reverse slip component during the rupture of the two high-frequency (2.0 Hz) subevents on the Kobe fault section. The resulting locations of the main subevents in space and time provided an interval of possible values of rupture velocity ranging between 2.65 km s−1 (that is, 80 per cent of the shear wave velocity) and 3.46 km s−1 (that is, the value of the shear wave velocity). This study emphasizes that S-wave polarization can be a useful tool to restrict the number of reliable starting models for iterative waveform inversions.

A classical analysis of proton collisions with ground-state and excited, aligned sodium targets

The dependence of electron capture and ionization processes on the pre-collision electronic distribution is examined for the systems primarily in the energy range 1 - 15 keV. Populations of the capture and ionization channels as well as the coherence of the post-collision electronic distribution of the capture product are formulated using the classical trajectory Monte Carlo (CTMC) method. Total capture and ionization cross sections arising from initially aligned Na(3p) targets exhibit transient behaviour near the velocity-matching energy of 5.7 keV. This observation is described in terms of anisotropy parameters; anisotropy effects are also analysed for the capture states n = 2, 3 and 4. In addition to the population manifold, we present theoretical calculations of the alignment parameter and the z-component of the dipole moment , in order to relate the alignment of the post-collision charge cloud to that of the initial Na(3s, , ) target states. The z-component of the cross product of the angular momentum and the Runge - Lenz vector is used to describe the orientation of the post-collision product generated from the aligned Na(, ) pre-collision reactants.