Search results for "Anisotropy"
showing 10 items of 912 documents
Magnetic excitations in TbP under hydrostatic pressure
1982
Singlet ground state magnets still attract much attention. In these systems magnetic ordering occurs via the polarization of the ground state, and noticeable dispersion of well defined excitations is expected in systems where the exchange coupling is about equal to the crystal field energy. In addition, the two singlet-triplet systems PrSbl and TbP2 where single crystals are available and which have been studied in detail showed a pronounced splitting of the Г1–Г4 magnetic excitations where the triple degeneracy was lifted along [100] and [011] by a strong anisotropy of the exchange.
Influence of rotational diffusion on the electric field induced effect on the fluorescence spectrum of diluted solutions I. Theory and numerical simu…
1997
Abstract The theory for the calculation of excited state dipole moments from electrooptical emission measurements, developed by Baumann and Deckers (Ber. Bunsenges. Phys. Chem. 81 (1977) 786) presupposes a Boltzmann distribution for the emitting molecules. Using the anisotropic rotational diffusion model and taking into account all important electric field induced effects, we derive equations that describe quantitatively the electric field effect on the fluorescence of an ensemble of solute rigid molecules which are not yet equilibrated with respect to their orientation when emitting. Numerical simulations are performed to compare the general case and the limiting case of a prevailing Boltz…
Residual fluctuations in the microwave background at large angular scales: Revision of the Sachs-Wolfe effect
1993
In this paper we revise the Sachs-Wolfe (SW) computation of large-scale an isotropies of the microwave background temperature, taking into account the properties of the metrics admitting an isotropic distribution of collisionless photons. We show that the metric used by SW belongs to the aforementioned class, and conclude that the microwave background (once the dipolar anisotropy has been subtracted) should now be isotropic at large angular scales, provided that it was isotropic on the last scattering surface and assuming that the growing mode of a pressureless Einstein-de Sitter perturbation is a good description of the metric.
Step-Edge Induced Anisotropic Domain-Wall Propagation
1999
We report the observation of anisotropic domain-wall propagation in ultrathin magnetic films with perpendicular anisotropy. A controlled density of step edges was introduced which allowed us to quantify its influence on the domain-wall pinning. For a sawtooth arrangement of the step edges the corresponding wall movement resulted in triangular shaped domains. All aspects of this anisotropic domain-wall evolution could be reproduced by a simulation based on a modified Ginzburg-Landau-type soft-spin model.
Anisotropy and memory during cage breaking events close to a wall
2016
The slow dynamics in a glassy hard-sphere system is dominated by cage breaking events, i.e., rearrangements where a particle escapes from the cage formed by its neighboring particles. We study such events for an overdamped colloidal system by the means of Brownian dynamics simulations. While it is difficult to relate cage breaking events to structural mean field results in bulk, we show that the microscopic dynamics of particles close to a wall can be related to the anisotropic two-particle density. In particular, we study cage-breaking trajectories, mean forces on a tracked particle, and the impact of the history of trajectories. Based on our simulation results, we further construct two di…
Energy spectrum and transport properties of the two-dimensional t-J model
1992
Abstract The formation of a ferromagnetically ordered region around a hole in the two-dimensional t-J model is investigated. The energy bands characterized by different values of the z-component of the total spin are analysed. A strong anisotropy of the lower-energy bands is found. For intermediate coupling of additionally included optical phonons, this anisotropy leads to a large polaronic state with an anisotropic envelope oriented along the plane diagonals. In the strong-coupling case the competition between the hole-magnon and the hole-phonon interactions prevents the formation of ferrons. Owing to the large effective mass in both cases, the hole transport takes place via hopping, with …
Non-equilibrium thermodynamics analysis of rotating counterflow superfluid turbulence
2010
In two previous papers two evolution equations for the vortex line density $L$, proposed by Vinen, were generalized to rotating superfluid turbulence and compared with each other. Here, the already generalized alternative Vinen equation is extended to the case in which counterflow and rotation are not collinear. Then, the obtained equation is considered from the viewpoint of non-equilibrium thermodynamics. According with this formalism, the compatibility between this evolution equation for $L$ and that one for the velocity of the superfluid component is studied. The compatibility condition requires the presence of a new term dependent on the anisotropy of the tangle, which indicates how the…
Interpreting deviations between AR-VTG and GR
2019
The cosmic microwave background (CMB) anisotropies predicted by two cosmological models are compared, one of them is the standard model of general relativity with cold dark matter and cosmological constant, whereas the second model is based on a consistent vector-tensor theory of gravitation explaining solar system and cosmological observations. It is proved that the resulting differences — between the anisotropies of both models — are due to the so-called late integrated Sachs–Wolfe effect and, consequently, cross-correlations between maps of CMB temperatures and tracers of the dark matter distribution could be used in future to select one of the above models. The role of reionization is …
Lens Effect and CMB Anisotropies: Deviations from Gaussianity
2003
The CMB sky can be seen as the superimposition of two components, one of them is the temperature distribution in the absence of lensing and the other one is the correction caused by lensing. In the model under consideration, the first of these components is Gaussian, but the second is not. Numerical methods to calculate angular correlations in the lens component are designed and tested. Some of these correlations are estimated. Deviations from Gaussianity are confirmed.