Periodic giant-persistent current in sharp pulses on a ring

We show here a mesoscopic device based on a narrow ring containing an electron. In the device, an amount of energy is stored in advance. Similar to the pendulum, an exact periodic motion of the electron is thereby initiated afterward. The motion appears as a series of sharp pulses, and is in nature different from the well known Aharonov-Bohm (A-B) oscillation. In particular, the pulses of current can be tuned to be very strong (say, more than two orders stronger than the usual A-B current). Related theory and numerical results are presented.Comment: 5 pages, 5 figure

Elementary modes of excitation caused by the quadratic Zeeman term and the sensitivity of spin structures of small spin-2 condensates against the magnetic field

The response of spin-2 small condensates to an external magnetic field $B$ is studied. The parameters of the interaction are considered as variable. The emphasis is placed on clarifying the modes of excitation caused by the quadratic Zeeman term. The theoretical method used is beyond the mean field theory. A set of eigenstates with the $U(5)\supset SO(5)\supset SO(3)$ symmetry is introduced to facilitate the analysis. To obtain a quantitative evaluation on the response, the fidelity susceptibility and the $B$ -dependent average populations of spin-components have been calculated. Mostly the particle number N=30 is assumed. The effect with a larger or smaller $N$ is also considered. It was found that the sensitivity of the response depends strongly both on the interaction and on the inherent symmetry.Comment: 9 pages, 7 figure

An overview on nonlinear porous flow in low permeability porous media

AbstractThis paper gives an overview on nonlinear porous flow in low permeability porous media, reveals the microscopic mechanisms of flows, and clarifies properties of porous flow fluids. It shows that, deviating from Darcy's linear law, the porous flow characteristics obey a nonlinear law in a low-permeability porous medium, and the viscosity of the porous flow fluid and the permeability values of water and oil are not constants. Based on these characters, a new porous flow model, which can better describe low permeability reservoir, is established. This model can describe various patterns of porous flow, as Darcy's linear law does. All the parameters involved in the model, having definite physical meanings, can be obtained directly from the experiments