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Anisotropic Models (anisotropic + models)
Selected AbstractsAnomalous phases exceeding 90° in magnetotellurics: anisotropic model studies and a field exampleGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2003Wiebke Heise SUMMARY A study of synthetic anisotropic models that explain phases exceeding 90° in magnetotellurics is presented. The basic model comprises an anisotropic layer overlain by a shallow (local) anisotropic block, with both structures inserted in a 2-D model. The 2-D strike and the anisotropy strikes (layer and block) differ. The influence of the following parameters was analysed: anisotropy strike, geometry of the block and the layer, and anisotropy ratios of the block and the layer. We show that, according to this model, the anomalous phase effect is limited to those sites above the shallow block and does not influence the regional structure, which can therefore be recovered. These results were applied to field data from a magnetotelluric profile in SW Iberia where phases greater than 90° occurred in an area in which alternating bands of schist and graphite-rich blackschists crop out, giving rise to strong macroanisotropy. [source] New anisotropic models from isotropic solutionsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 1 2006S. D. Maharaj Abstract We establish an algorithm that produces a new solution to the Einstein field equations, with an anisotropic matter distribution, from a given seed isotropic solution. The new solution is expressed in terms of integrals of known functions, and the integration can be completed in principle. The applicability of this technique is demonstrated by generating anisotropic isothermal spheres and anisotropic constant density Schwarzschild spheres. Both of these solutions are expressed in closed form in terms of elementary functions, and this facilitates physical analysis. Copyright © 2005 John Wiley & Sons, Ltd. [source] The origin and formation of cuspy density profiles through violent relaxation of stellar systemsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2000S. Hozumi It is shown that the cuspy density distributions observed in the cores of elliptical galaxies can be realized by dissipationless gravitational collapse. The initial models consist of power-law density spheres such as ,,r,1 with anisotropic velocity dispersions. Collapse simulations are carried out by integrating the collisionless Boltzmann equation directly, on the assumption of spherical symmetry. From the results obtained, the extent of constant density cores, formed through violent relaxation, decreases as the velocity anisotropy increases radially, and practically disappears for extremely radially anisotropic models. As a result, the relaxed density distributions become more cuspy with increasing radial velocity anisotropy. It is thus concluded that the velocity anisotropy could be a key ingredient for the formation of density cusps in a dissipationless collapse picture. The velocity dispersions increase with radius in the cores according to the nearly power-law density distributions. The power-law index, n, of the density profiles, defined as ,,r,n, changes from n,2.1 at intermediate radii to a shallower power than n,2.1 toward the centre. This density bend can be explained from our postulated local phase-space constraint that the phase-space density accessible to the relaxed state is determined at each radius by the maximum phase-space density of the initial state. [source] The conformal status of o = -3/2 Brans-Dicke cosmologyANNALEN DER PHYSIK, Issue 4 2007M.P. Da, browski Abstract Following recent fit of supernovae data to Brans-Dicke theory which favours the model with o = - 3/2 [1] we discuss the status of this special case of Brans-Dicke cosmology in both isotropic and anisotropic framework. It emerges that the limit o = -3/2 is consistent only with the vacuum field equations and it makes such a Brans-Dicke theory conformally invariant. Then it is an example of the conformal relativity theory which allows the invariance with respect to conformal transformations of the metric. Besides, Brans-Dicke theory with o = -3/2 gives a border between a standard scalar field model and a ghost/phantom model. In this paper we show that in o = -3/2 Brans-Dicke theory, i.e., in the conformal relativity there are no isotropic Friedmann solutions of non-zero spatial curvature except for k=-1 case. Further we show that this k=-1 case, after the conformal transformation into the Einstein frame, is just the Milne universe and, as such, it is equivalent to Minkowski spacetime. It generally means that only flat models are fully consistent with the field equations. On the other hand, it is shown explicitly that the anisotropic non-zero spatial curvature models of Kantowski-Sachs type are admissible in o = -3/2 Brans-Dicke theory. It then seems that an additional scale factor which appears in anisotropic models gives an extra deegre of freedom and makes it less restrictive than in an isotropic Friedmann case. [source] | ||||||||||