Abstract:
Recently novel current-driven resonant states characterized by the $\pi$-phase kinks were proposed in the coupled sine-Gordon equation. In these states hysteresis behavior is observed with respect to the application process of current, and such behavior is due to nonlinearity in the sine term. Varying strength of the sine term, there exists a critical strength for the hysteresis behavior and the amplitude of the sine term coincides with the applied current at the critical strength.

Abstract:
Current-driven magnetic domain wall motion is demonstrated in the quaternary ferromagnetic semiconductor (Ga,Mn)(As,P) at temperatures well below the ferromagnetic transition temperature, with critical currents of the order 10^5Acm^-2. This is enabled by a much weaker domain wall pinning compared to (Ga,Mn)As layers grown on a strain-relaxed buffer layer. The critical current is shown to be comparable with theoretical predictions. The wide temperature range over which domain wall motion can be achieved indicates that this is a promising system for developing an improved understanding of spin-transfer torque in systems with strong spin-orbit interaction.

Abstract:
We prove nonequilibrium fluctuations for the boundary driven symmetric simple exclusion process. We deduce from this result the stationary fluctuations.

Abstract:
We investigate stationary nonequilibrium states of systems of particles moving according to Hamiltonian dynamics with specified potentials. The systems are driven away from equilibrium by Maxwell demon ``reflection rules'' at the walls. These deterministic rules conserve energy but not phase space volume, and the resulting global dynamics may or may not be time reversible (or even invertible). Using rules designed to simulate moving walls we can obtain a stationary shear flow. Assuming that for macroscopic systems this flow satisfies the Navier-Stokes equations, we compare the hydrodynamic entropy production with the average rate of phase space volume compression. We find that they are equal when the velocity distribution of particles incident on the walls is a local Maxwellian. An argument for a general equality of this kind, based on the assumption of local thermodynamic equilibrium, is given. Molecular dynamic simulations of hard disks in a channel produce a steady shear flow with the predicted behavior.

Abstract:
A Keldysh-contour effective field theory is derived for magnetic vortices in the presence of current flow. The effect of adiabatic and non-adiabatic spin transfer torques on vortex motion is highlighted. Similarities to and differences from the superconducting case are presented and explained. Current flow across a magnetically ordered state is shown to lead to a defect-unbinding phase transition which is intrinsically nonequilibrium in the sense of not being driven by a variation in effective temperature. The dependence of the density of vortices on the current density is determined.

Abstract:
We have investigated the influence of velocity shear and a radial density profile on the spatial development of the current driven kink instability along helically magnetized relativistic jets via three-dimensional relativistic magnetohydrodynamic simulations. In this study, we use a non-periodic computational box, the jet flow is initially established across the computational grid, and a precessional perturbation at the inlet triggers growth of the kink instability. If the velocity shear radius is located inside the characteristic radius of the helical magnetic field, a static non-propagating current driven kink is excited as the perturbation propagates down the jet. Temporal growth disrupts the initial flow across the computational grid not too far from the inlet. On the other hand, if the velocity shear radius is outside the characteristic radius of the helical magnetic field, the kink is advected with the flow and grows spatially down the jet. In this case flow is maintained to much larger distances from the inlet. The effect of different radial density profiles is more subtle. When the density increases with radius, the kink appears to saturate by the end of the simulation without apparent disruption of the helical twist. This behavior suggests that relativistic jets consisting of a tenuous spine surrounded by a denser medium with a velocity shear radius outside the radius of maximum toroidal magnetic field have a relatively stable configuration.

Abstract:
We examine the entropy of stationary nonequilibrium measures of boundary driven symmetric simple exclusion processes. In contrast with the Gibbs--Shannon entropy \cite{B, DLS2}, the entropy of nonequilibrium stationary states differs from the entropy of local equilibrium states.

Abstract:
We devise a microscopic model for the emergence of a collision-induced, fermionic atomic current across a tilted optical lattice. Tuning the - experimentally controllable - parameters of the microscopic dynamics allows to switch from Ohmic to negative differential conductance.

Abstract:
We present fluid dynamics videos of the pulsing dynamics and the resulting fluid flow generated by the upside down jellyfish, Cassiopea spp. Medusae of this genus are unusual in that they typically rest upside down on the ocean floor and pulse their bells to generate feeding currents, only swimming when significantly disturbed. The pulsing kinematics and fluid flow around these upside down jellyfish is investigated using a combination of videography, flow visualization, and numerical simulation. Significant mixing occurs around and directly above the oral arms and secondary mouths. Numerical simulations using the immersed boundary method with a porous layer representing the oral arms agree with the experimental results. The simulations also suggest that the presence of porous oral arms induce net horizontal flow towards the bell. Coherent vortex rings are not seen in the wake above the jellyfish, but starting and stopping vortices are observed before breaking up as they pass through the elaborate oral arms (if extended).