3 research outputs found
Aging without disorder on long time scales
We study the Metropolis dynamics of a simple spin system without disorder,
which exhibits glassy dynamics at low temperatures. We use an implementation of
the algorithm of Bortz, Kalos and Lebowitz \cite{bortz}. This method turns out
to be very efficient for the study of glassy systems, which get trapped in
local minima on many different time scales. We find strong evidence of aging
effects at low temperatures. We relate these effects to the distribution
function of the trapping times of single configurations.Comment: 8 pages Revtex, 7 figures uuencoded (Revised version: the figures are
now present
South-polar features on Venus similar to those near the north pole
Venus has no seasons, slow rotation and a very massive atmosphere, which is mainly carbon dioxide with clouds primarily of sulphuric acid droplets. Infrared observations by previous missions to Venus revealed a bright 'dipole' feature surrounded by a cold 'collar' at its north pole (1–4). The polar dipole is a 'double-eye' feature at the centre of a vast vortex that rotates around the pole, and is possibly associated with rapid downwelling. The polar cold collar is a wide, shallow river of cold air that circulates around the polar vortex. One outstanding question has been whether the global circulation was symmetric, such that a dipole feature existed at the south pole. Here we report observations of Venus' south-polar region, where we have seen clouds with morphology much like those around the north pole, but rotating somewhat faster than the northern dipole. The vortex may extend down to the lower cloud layers that lie at about 50km height and perhaps deeper. The spectroscopic properties of the clouds around the south pole are compatible with a sulphuric acid composition