7,924 research outputs found
Theory of the Spatio-Temporal Dynamics of Transport Bifurcations
The development and time evolution of a transport barrier in a magnetically
confined plasma with non-monotonic, nonlinear dependence of the anomalous flux
on mean gradients is analyzed. Upon consideration of both the spatial
inhomogeneity and the gradient nonlinearity of the transport coefficient, we
find that the transition develops as a bifurcation front with radially
propagating discontinuity in local gradient. The spatial location of the
transport barrier as a function of input flux is calculated. The analysis
indicates that for powers slightly above threshold, the barrier location
where is the local transition
power threshold and is the neoclassical diffusivity . This result
suggests a simple explanation of the high disruptivity observed in reversed
shear plasmas. The basic conclusions of this theory are insensitive to the
details of the local transport model.Comment: 21 page Tex file, 10 postscript file
Crossed product of a C*-algebra by a semigroup of endomorphisms generated by partial isometries
The paper presents a construction of the crossed product of a C*-algebra by a
semigroup of endomorphisms generated by partial isometries.Comment: 22 page
Shape transformations in rotating ferrofluid drops
Floating drops of magnetic fluid can be brought into rotation by applying a
rotating magnetic field. We report theoretical and experimental results on the
transition from a spheroid equilibrium shape to non-axissymmetrical three-axes
ellipsoids at certain values of the external field strength. The transitions
are continuous for small values of the magnetic susceptibility and show
hysteresis for larger ones. In the non-axissymmetric shape the rotational
motion of the drop consists of a vortical flow inside the drop combined with a
slow rotation of the shape. Nonlinear magnetization laws are crucial to obtain
quantitative agreement between theory and experiment.Comment: 4 pages, 3 figure
Stochastic Approach to Flat Direction during Inflation
We revisit the time evolution of a flat and non-flat direction system during
inflation. In order to take into account quantum noises in the analysis, we
base on stochastic formalism and solve coupled Langevin equations numerically.
We focus on a class of models in which tree-level Hubble-induced mass is not
generated. Although the non-flat directions can block the growth of the flat
direction's variance in principle, the blocking effects are suppressed by the
effective masses of the non-flat directions. We find that the fate of the flat
direction during inflation is determined by one-loop radiative corrections and
non-renormalizable terms as usually considered, if we remove the zero-point
fluctuation from the noise terms.Comment: 17 pages, 4 figures, v2: minor corrections made, published in JCA
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