34,979 research outputs found
QSES's and the Quantum Jump
The stochastic methods in Hilbert space have been used both from a
fundamental and a practical point of view. The result we report here concerns
only the idea of applying these methods to model the evolution of quantum
systems and does not enter into the question of their fundamental or practical
status. It can be easily stated as follows: Once a quantum stochastic evolution
scheme is assumed, the incompatibility between the Markov property and the
notion of quantum jump is rapidly established.Comment: LaTeX2e, 3 pages, no figures. Included in the Proceedings of the 3rd
Workshop on Mysteries, Puzzles and Paradoxes in Quantum Mechanics, Gargnano,
Italy, September 17-23, 200
Energy spectrum, dissipation and spatial structures in reduced Hall magnetohydrodynamic
We analyze the effect of the Hall term in the magnetohydrodynamic turbulence
under a strong externally supported magnetic field, seeing how this changes the
energy cascade, the characteristic scales of the flow and the dynamics of
global magnitudes, with particular interest in the dissipation.
Numerical simulations of freely evolving three-dimensional reduced
magnetohydrodynamics (RHMHD) are performed, for different values of the Hall
parameter (the ratio of the ion skin depth to the macroscopic scale of the
turbulence) controlling the impact of the Hall term. The Hall effect modifies
the transfer of energy across scales, slowing down the transfer of energy from
the large scales up to the Hall scale (ion skin depth) and carrying faster the
energy from the Hall scale to smaller scales. The final outcome is an effective
shift of the dissipation scale to larger scales but also a development of
smaller scales. Current sheets (fundamental structures for energy dissipation)
are affected in two ways by increasing the Hall effect, with a widening but at
the same time generating an internal structure within them. In the case where
the Hall term is sufficiently intense, the current sheet is fully delocalized.
The effect appears to reduce impulsive effects in the flow, making it less
intermittent.Comment: 17 pages, 10 figure
- …