tsujigiri

The editorial comments of Chris and James, covering the news, science, religion, politics and culture.

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Saturday, October 29, 2005

Cold Spanish Rubidium

Capital:
Moreno and co-workers modelled a thin film that contained an array of slits that were 50 nm wide and separated by 800 nm. Since the de Broglie wavelength of the atoms was around 800 nm, transmission through the slits should have been negligible. However, by carefully tuning the van der Waals interactions between the atoms and the surface, and also the dipolar repulsion created by optical fields in the structure, they showed that 100% of the atoms should be able to pass through the slits with the help of surface matter waves. These waves are the atomic analogue of surface plasmons and may appear when a dielectric surface presents a potential well for the atoms. They are running waves that are confined in the direction perpendicular to the surface but they propagate in the parallel direction.
In other news, I heard George Zaslavsky lecture on Thursday about the following:
In the gap between chaotic and regular dynamics, there exists pseudochaos that occurs due to much weaker dynamical instability. Despite the weakness of instability, pseudochaos can provide strongly anomalous transport, and particularly superdiffusion, of particles in fluids (pollutants in the ocean and atmosphere) and plasma devices (tokamak, stellarator). Fairly simple magnetic fields that can be expressed as analytic functions of (x,y,z) can result in extremely complicated topologies of field lines, which, in turn, induce chaotic and pseudochaotic dynamics of particles that are within the field volume. This effect is important in practice for such programs as controlled fusion.
At one point he mapped the 2-D paths of a billiard ball ricocheting around different enclosed courses to distinct toroids, and then extrapolated to something totally cool and totally over my head.

I need to know more about topology.