Irregular mixing due to a vortex pair interacting with a fixed vortex

The paper examines scalar advection caused by a point–vortex pair encountering a fixed point vortex in a uniform flow. The interaction produces two types of vortex motion. First is unbounded as the pair moves unrestrictedly after encountering the fixed vortex. The scalar exchanging between the pair's bubble and fixed vortex's neighbourhood is numerically estimated. Second is bounded as the pair's vortices periodically oscillate about the fixed vortex. The pair's periodic motion perturbs scalar motion causing a portion of scalar trajectories to manifest chaotic behaviour. We analyse scalar transport using Poincaré sections, which reveal regular and chaotic transport regions.     

Parametric resonance with a point-vortex pair in a nonstationary deformation flow

The movement of a pair of point vortices with arbitrary intensities, embedded in a nonstationary shear and rotational flow, is studied. The expression for the vorticity center is shown to be reduced to a Riccati equation. In the particular case of harmonic oscillations, parametric resonance, which results in unbounded motion of the vortex pair, is found and analyzed. Using the fast oscillation averaging, an analytical estimate for the main zone in the parametric space is obtained. With the help of numerical calculations, the reliability of the estimate is asserted and a family of the minor zones is obtained.     

Comparative study of heterogeneous magnetic state above TC in La0.82Sr0.18CoO3 cobaltite and La0.83Sr0.17MnO3 manganite

The magnetic, transport and structural properties are studied for La_0.83Sr_0.17MnO₃ and La_0.82Sr_0.18CoO₃ single crystals with nearly the same doping and the metallic ground state. Their comparisons have shown that ferromagnetic clusters originate in the paramagnetic matrix below Т^?>T_C in both samples and exhibit similar properties. This suggests the possible universality of such phenomena in doped mixed-valence oxides of transition metals with the perovskite-type structure. The cluster density increases on cooling and plays an important role on the physical properties of these systems. The differences in cluster evolutions and scenarios of their insulator–metal transitions are related to different magnetic behaviors of the matrixes in these crystals that is mainly due to distinct spin states of the Mn³⁺ and Co³⁺ ions.     

Melting of Two-Dimensional Systems: Dependence of the Type of Transition on the Radius of the Potential

In the framework of the two-dimensional melting theory based on the density functional approach, we use a Monte Carlo computer simulation to study melting of a two-dimensional hard disk system with a rectangular-well attraction potential. We show that depending on the attraction radius, the melting can occur via a single first-order transition as well as continuously in accordance with the Kosterlitz–Thouless–Halperin–Nelson–Young theory.     

Possible Scenarios of a Phase Transition from Isotropic Liquid to a Hexatic Phase in the Theory of Melting in Two-Dimensional Systems

Theoretical and Mathematical Physics - A two-stage process consisting of two continuous Berezinskii-Kosterlitz-Thouless-type transitions with an intermediate anisotropic liquid, a hexatic phase, is...     

Temperature Evolution of the Interaction of Relaxation Processes with Local Dynamics at Terahertz Frequencies in Polymers with Hydrogen Bonds

Physics of the Solid State - At terahertz frequencies, the torsional vibration motion is associated with dielectric relaxation in disordered solids with hydrogen bonds. The interaction between...     

Synthesis of GalNGcα1-3GalNAcα disaccharide and its interaction with human blood antibodies

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