123,841 research outputs found
A metric property of umbilic points
In the space of cubic forms of surfaces, regarded as a
-space and endowed with a natural invariant metric, the ratio of the volumes
of those representing umbilic points with negative to those with positive
indexes is evaluated in terms of the asymmetry of the metric, defined here. A
connection of this ratio with that reported by Berry and Hannay (1977) in the
domain of Statistical Physics, is discussed.Comment: 8 pages, 1 figur
Stabilizing Entangled States with Quasi-Local Quantum Dynamical Semigroups
We provide a solution to the problem of determining whether a target pure
state can be asymptotically prepared using dissipative Markovian dynamics under
fixed locality constraints. Beside recovering existing results for a large
class of physically relevant entangled states, our approach has the advantage
of providing an explicit stabilization test solely based on the input state and
constraints of the problem. Connections with the formalism of frustration-free
parent Hamiltonians are discussed, as well as control implementations in terms
of a switching output-feedback law.Comment: 11 pages, no figure
Burst statistics in Alcator C-Mod SOL turbulence
Bursty fluctuations in the scrape-off layer (SOL) of Alcator C-Mod have been
analyzed using gas puff imaging data. This reveals many of the same fluctuation
properties as Langmuir probe measurements, including normal distributed
fluctuations in the near SOL region while the far SOL plasma is dominated by
large amplitude bursts due to radial motion of blob-like structures.
Conditional averaging reveals burst wave forms with a fast rise and slow decay
and exponentially distributed waiting times. Based on this, a stochastic model
of burst dynamics is constructed. The model predicts that fluctuation
amplitudes should follow a Gamma distribution. This is shown to be a good
description of the gas puff imaging data, validating this aspect of the model.Comment: 8 pages, 6 figure
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