Domain-wall resistance in ferromagnetic (Ga,Mn)As

A series of microstructures designed to pin domain-walls (DWs) in (Ga,Mn)As with perpendicular magnetic anisotropy has been employed to determine extrinsic and intrinsic contributions to DW resistance. The former is explained quantitatively as resulting from a polarity change in the Hall electric field at DW. The latter is one order of magnitude greater than a term brought about by anisotropic magnetoresistance and is shown to be consistent with disorder-induced misstracing of the carrier spins subject to spatially varying magnetization

More on the Isomorphism SU(2)⊗SU(2)≅SO(4)SU(2)\otimes SU(2)\cong SO(4)

In this paper we revisit the isomorphism $SU(2)\otimes SU(2)\cong SO(4)$ to apply to some subjects in Quantum Computation and Mathematical Physics. The unitary matrix $Q$ by Makhlin giving the isomorphism as an adjoint action is studied and generalized from a different point of view. Some problems are also presented. In particular, the homogeneous manifold $SU(2n)/SO(2n)$ which characterizes entanglements in the case of $n=2$ is studied, and a clear-cut calculation of the universal Yang-Mills action in (hep-th/0602204) is given for the abelian case.Comment: Latex ; 19 pages ; 5 figures ; minor changes. To appear in International Journal of Geometric Methods in Modern Physics (vol.4, no.3

On the Magic Matrix by Makhlin and the B-C-H Formula in SO(4)

A closed expression to the Baker-Campbell-Hausdorff (B-C-H) formula in SO(4) is given by making use of the magic matrix by Makhlin. As far as we know this is the {\bf first nontrivial example} on (semi-) simple Lie groups summing up all terms in the B-C-H expansion.Comment: Latex ; 11 pages ; 1 figure ; minor changes. To appear in International Journal of Geometric Methods in Modern Physics (vol.4, no.5 or 6), 200

Design and Observation of Steep Reinforced Embankments

Using the design method proposed by R. A. Jewell et al. numerous steep reinforced embankments have been constructed in the authors’ home country since the year 1984. In fact these soil structures are built with the reinforcement of polymer grids (the so-called geogrids invented by F. B. Mercer of U.K.) which have a unique structural composition with high-tensile and low-ductility characteristics. This paper deals with first the development of steep reinforced soil structures and their design method, and then introduces a well-documented case history of steep reinforced embankment. The authors propose a current design method developed on the basis of the findings obtained from the observations at several steep reinforced embankments including the present one of the case history. And finally an ultimate seismic-design method for steep reinforced embankment adopted recently in Japan is presented

Velocity of domain-wall motion induced by electrical current in a ferromagnetic semiconductor (Ga,Mn)As

Current-induced domain-wall motion with velocity spanning over five orders of magnitude up to 22 m/s has been observed by magneto-optical Kerr effect in (Ga,Mn)As with perpendicular magnetic anisotropy. The data are employed to verify theories of spin-transfer by the Slonczewski-like mechanism as well as by the torque resulting from spin-flip transitions in the domain-wall region. Evidence for domain-wall creep at low currents is found.Comment: 5 pages, 3 figure

Seismic Response and Liquefaction Analysis by an Approximate Method

Presented is a simplified procedure for performing the dynamic effective stress analysis. An equivalent linear method is applied to the procedure. It is assumed, in this method, that the variations of the shear modulus and damping factor due to strain level and effective stress are independent one another. That is, firstly the total stress analysis is done in order to obtain the effective strain. Then the effective stress analysis is carried out and the moduli are varied due to the variation of the effective stress only. The accuracy of the result is checked by comparing it with that of nonlinear solution

Thermal Effects in the dynamics of disordered elastic systems

Many seemingly different macroscopic systems (magnets, ferroelectrics, CDW, vortices,..) can be described as generic disordered elastic systems. Understanding their static and dynamics thus poses challenging problems both from the point of view of fundamental physics and of practical applications. Despite important progress many questions remain open. In particular the temperature has drastic effects on the way these systems respond to an external force. We address here the important question of the thermal effect close to depinning, and whether these effects can be understood in the analogy with standard critical phenomena, analogy so useful to understand the zero temperature case. We show that close to the depinning force temperature leads to a rounding of the depinning transition and compute the corresponding exponent. In addition, using a novel algorithm it is possible to study precisely the behavior close to depinning, and to show that the commonly accepted analogy of the depinning with a critical phenomenon does not fully hold, since no divergent lengthscale exists in the steady state properties of the line below the depinning threshold.Comment: Proceedings of the International Workshop on Electronic Crystals, Cargese(2008