13 research outputs found
Duality and exact results for conductivity of 2D isotropic heterophase systems in magnetic field
Using a fact that the effective conductivity sigma_{e} of 2D random heterophase systems in the orthogonal magnetic field is transformed under some subgroup of the linear fractional group, connected with a group of linear transformations of two conserved currents, the exact values for sigma_{e} of isotropic heterophase systems are found. As known, for binary (N=2) systems a determination of exact values of both conductivities (diagonal sigma_{ed} and transverse Hall sigma_{et}) is possible only at equal phase concentrations and arbitrary values of partial conductivities. For heterophase (N > 2) systems this method gives exact values of effective conductivities, when their partial conductivities belong to some hypersurfaces in the space of these partial conductivities and the phase concentrations are pairwise equal. In all these cases sigma_e does not depend on phase concentrations. The complete, 3-parametric, explicit transformation, connecting sigma_e in binary systems with a magnetic field and without it, is constructe
Planar isotropic two-phase systemsin perpendicular magnetic field: effective conductivity
Three explicit approximate expressions for the effective conductivity sigma_e
of various planar isotropic two-phase systems in a magnetic field are obtained
using the dual linear fractional transformation, connecting sigma_e of these
systems with and without magnetic field. The obtained results are applicable
for two-phase systems (regular and nonregular as well as random), satisfying
the symmetry and self-duality conditions, and allow to describe sigma_e of
various two-dimensional and layered inhomogeneous media at arbitrary phase
concentrations and magnetic fields. All these results admit a direct
experimental checking.Comment: 10 pages, Latex2e, 3 figure
Duality and exact results for conductivity of 2D isotropic heterophase systems in magnetic field
Using a fact that the effective conductivity sigma_{e} of 2D random
heterophase systems in the orthogonal magnetic field is transformed under some
subgroup of the linear fractional group, connected with a group of linear
transformations of two conserved currents, the exact values for sigma_{e} of
isotropic heterophase systems are found. As known, for binary (N=2) systems a
determination of exact values of both conductivities (diagonal sigma_{ed} and
transverse Hall sigma_{et}) is possible only at equal phase concentrations and
arbitrary values of partial conductivities. For heterophase (N > 2) systems
this method gives exact values of effective conductivities, when their partial
conductivities belong to some hypersurfaces in the space of these partial
conductivities and the phase concentrations are pairwise equal. In all these
cases sigma_e does not depend on phase concentrations. The complete,
3-parametric, explicit transformation, connecting sigma_e in binary systems
with a magnetic field and without it, is constructedComment: 15 pages, 3 figures, Latex2
Large linear magnetoresistivity in strongly inhomogeneous planar and layered systems
Explicit expressions for magnetoresistance of planar and layered strongly
inhomogeneous two-phase systems are obtained, using exact dual transformation,
connecting effective conductivities of in-plane isotropic two-phase systems
with and without magnetic field. These expressions allow to describe the
magnetoresistance of various inhomogeneous media at arbitrary concentrations
and magnetic fields . All expressions show large linear
magnetoresistance effect with different dependencies on the phase
concentrations. The corresponding plots of the - and -dependencies of
are represented for various values, respectively, of magnetic field
and concentrations at some values of inhomogeneity parameter. The obtained
results show a remarkable similarity with the existing experimental data on
linear magnetoresistance in silver chalcogenides A possible
physical explanation of this similarity is proposed. It is shown that the
random, stripe type, structures of inhomogeneities are the most suitable for a
fabrication of magnetic sensors and a storage of information at room
temperatures.Comment: 12 pages, 2 figures, Latex2
The Misfit Strain Critical Point in the 3D Phase Diagrams of Cuprates
At the time of writing, data have been reported on several hundred different
cuprates materials, of which a substantial fraction show superconductivity at
temperatures as high as 130 K. The existence of several competing phases with
comparable energy shows up in different ways in different materials, therefore
it has not been possible to converge toward a universal theory for high Tc
superconductivity. With the aim to find a unified description the
Aeppli-Bianconi 3D phase diagram of cuprates has been proposed where the
superlattice misfit strain (eta) is the third variable beyond doping (delta)
and temperature T. The 3D phase diagrams for the magnetic order, and for the
superconducting order extended to all cuprates families are described. We
propose a formula able to describe the Tc (delta,eta) surface, this permits to
identify the stripe quantum critical point at (delta)c=1/8 and (eta)c =7percent
which is associated with the incommensurate to commensurate stripe phase
transition, controlled by the misfit strain.Comment: 12 pages and 2 figure
Harmonic map analysis of SU(N) gravitating skyrmions
In this paper the SU(N) Einstein-Skyrme system is considered. We express the chiral field [which is not a simple embedding of the SU(2) field] in terms of harmonic maps. In this way, SU(N) spherical symmetric equations can be obtained easily for any N and the gravitating Skyrmion solutions of these equations can be studied. In particular, the SU(3) case is considered in detail and three different types of gravitating Skyrmions with topological charge four, two, and zero, respectively, are constructed numerically. Note that the configuration with zero topological charge corresponds to mixtures of Skyrmions and anti-Skyrmions