Diffusion in a time-dependent external field

Diffusion in a time-dependent external field.

The problem of diffusion in a time-dependent (and generally inhomogeneous) external field is considered on the basis of a generalized master equation with two times, introduced by Trigger and co-authors [S. A. Trigger, G. J. F. van Heijst, and P. P. J. M. Schram, Physica A 347, 77 (2005); J. Phys.: Conf. Ser. 11, 37 (2005)]. We consider the case of the quasi-Fokker-Planck approximation, when th...

Quantum response to time-dependent external field

Recently, explicit real time dynamics has been studied in various systems. These quantum mechanical dynamics could provide new recipes in information processing. Here, we study quantum dynamics under time dependent external field. In particular, we compare the thermal and quantum fluctuation in the transverse Ising model. Moreover we study other types of quantum fluctuations, e.g. effects of th...

Pulsed-field-gradient measurements of time-dependent gas diffusion.

Pulsed-field-gradient NMR techniques are demonstrated for measurements of time-dependent gas diffusion. The standard PGSE technique and variants, applied to a free gas mixture of thermally polarized xenon and O2, are found to provide a reproducible measure of the xenon diffusion coefficient (5.71 x 10(-6) m2 s-1 for 1 atm of pure xenon), in excellent agreement with previous, non-NMR measurement...

Time-dependent diffusion in A-stars

Each time diffusion of elements is invoked in explaining abundance anomalies in a star, this supposes implicitly that a stratification process is in progress somewhere in that star. This means also, that the element abundances can still be evolving according to the star’s age and fundamental parameters. Moreover, it has been shown that the superficial abundances may have complex temporal behavi...

Spin Diffusion Measurements: Spin Echoes in the Presence of a Time Dependent Field Gradient