We show that the transverse components of spin current in a ferromagnet is linked to an off diagonal spin component of the transmission matrix at interfaces;it has little to do with the mismatch of band structures between dissimilar metals. When we take account of this component,not considered in prior analyses, we find spin torque comes from a region of at lease 3 nm around an interface. It occurs when one drives an electric current across a multilayered structure in which the magnetic layers are noncollinear. The central idea behind the switching is that when the spin polarized current that develops in a fixed ferromagnetic layer of a multilayered structure impinges on a second noncollinear free magnetic layer the component of the spin current transverse to the magnetization is absorbed. As one assumes the conservation of spin angular momentum this creates the torque on the background magnetization to switch it. One of the unresolved issues is the length scale over which the transverse component of the spin current is absorbed and what material parameters controls it. Here, we point out, that the detail of the transverse spin near the interface does matter in determining the spin transfer torque. The reason is that transport is inherently non-local so that the incident spin polarization at an interface does depend on the detail of the transverse spin accumulation even if this length scale is small, i.e., one must include transverse pin accumulation. Mathematically, the boundary condition solely from the vanishing transverse spin density in ferromagnets is not sufficient to determine the spin torque. If we write the boundary condition to the distribution function on the two sides of an interface, we have found that the truncation of the transmission matrix to a diagonal matrix in spin space misses key relations between the spinor distribution functions on the two sides of an interface, and thus the transport across the entire structure is unable to be self-consistently determined.We recently found a possible mechanism by which one can inject off diagonal spin distributions into each sheet of the spin split Fermi surface of a magnetic layer, i.e., in the presence a current a spin flip potential can exist at interfaces in noncollinear magnetic multilayers. [3] This additional scattering excites the transverse components of spin currents in magnetic layers that are found by adopting the Boltzmann equation's definition of spin current and then we find there is no discontinuity in the spin current at an interface between two dissimilar layers. This transverse current is different from that evaluated from equilibrium states; [4,5] they complement one another but the existence of the latter does not negate the former. We evaluate the relevant parameters over which this component is absorbed by using ab-initio band structure calculations and find the characteristic length scale in a typical 3d transition-metal ferromagnet(Co) is 3 nm. This is an order of magnitude greater than that found in prior analysis which evaluat...

It is believed by the majority today that the efficient market hypothesis is imperfect because of market irrationality. Using the physical concepts and mathematical structures of quantum mechanics, we construct an econophysics framework for the stock market, based on which we analogously map massive numbers of single stocks into a reservoir consisting of many quantum harmonic oscillators and their stock index into a typical quantum open system-a quantum Brownian particle. In particular, the irrationality of stock transactions is quantitatively considered as the Planck constant within Heisenberg's uncertainty relationship of quantum mechanics in an analogous manner. We analyze real stock data of Shanghai Stock Exchange of China and investigate fat-tail phenomena and non-Markovian behaviors of the stock index with the assistance of the quantum Brownian motion model, thereby interpreting and studying the limitations of the classical Brownian motion model for the efficient market hypothesis from a new perspective of quantum open system dynamics.

Ultralight bosons such as axion-like particles are viable candidates for dark matter. They can form stable, macroscopic field configurations in the form of topological defects that could concentrate the dark matter density into many distinct, compact spatial regions that are small compared with the Galaxy but much larger than the Earth. Here we report the results of the search for transient signals from the domain walls of axion-like particles by using the global network of optical magnetometers for exotic (GNOME) physics searches. We search the data, consisting of correlated measurements from optical atomic magnetometers located in laboratories all over the world, for patterns of signals propagating through the network consistent with domain walls. The analysis of these data from a continuous month-long operation of GNOME finds no statistically significant signals, thus placing experimental constraints on such dark matter scenarios.

We present the formulation of a two-phase, electrical-hydrodynamic model for the description of electrorheological fluid dynamics, based on the Onsager principle of minimum energy dissipation. By considering the energetics of (induced) dipole-dipole interaction between the solid particles in terms of a field variable n( x), we employ the Onsager principle to derive the relevant coupled hydrodynamic equations, together with a continuity equation for n( x). Numerical solution of the relevant equations yields predictions that display very realistic behaviors as seen experimentally. In particular, we show that while the predicted results have features that resemble Bingham fluids, there can be important differences. For example, the yield stress obtained by extrapolating the shear rate to zero is 30-40% lower than that obtained from the maximum of the stress-strain relation. Moreover, for the conventional electrode configuration where the field is perpendicular to the shearing direction, there is very clear shearing-thinning effect that has been seen experimentally. §1. Introduction Electrorheology (ER) denotes the electric field-induced variation in the rheological characteristics of complex fluids. ER fluid 1)-10) usually consists of solid particles dispersed in an insulating liquid. Owing to the dielectric constant contrast between the solid particles and the liquid, each solid particle would be polarized under an electrostatic field, with an effective dipole moment. The resulting (induced) dipoledipole interaction means that the particles tend to aggregate and form columns along the applied field direction. The formation of columns is the reason why the highfield state of an ER fluid exhibits an increased viscosity or even solid-like behavior, able to sustain shear in the direction perpendicular to the applied electric field. The rheological variation is reversible when the field is removed. The response time can be as short as a few milliseconds. Due to such marvelous features, ER fluid can serve as an electric-mechanical interface, and when coupled with sensors to trigger the electric field, can turn many devices such as clutches, valves, dampers etc. into active mechanical elements 2), 3) capable of responding to environmental variationshence the denotation of "smart" fluid.When an ER fluid is placed between two parallel conducting plates and sheared in the Couette-flow configuration, the columns formed under the applied field can break and re-attach, leading to complex dynamics. In addition, under high shear rates the columns can tilt relative to the electric field direction, further weakening its resistance to shear. If the shear is achieved by a small but finite displacement of the top plate relative to the bottom plate, then the ER fluid (under an applied field) can exhibit elastic behavior up to a critical value of the displacement. 1) Thus