48 research outputs found
Decoherence within a simple Model for the Environment
This article examines the decoherence of a macroscopic body using a simple
model of the environment and following the evolution of the pure state for the
whole system. We found that decoherence occurs for very general initial
conditions and were able to confirm a number of widely accepted features of the
process.Comment: 13 pages, LaTex, no figures. To appear on Found. Phys. Lett
The interpretation of the field angle dependence of the critical current in defect-engineered superconductors
We apply the vortex path model of critical currents to a comprehensive
analysis of contemporary data on defect-engineered superconductors, showing
that it provides a consistent and detailed interpretation of the experimental
data for a diverse range of materials. We address the question of whether
electron mass anisotropy plays a role of any consequence in determining the
form of this data and conclude that it does not. By abandoning this false
interpretation of the data, we are able to make significant progress in
understanding the real origin of the observed behavior. In particular, we are
able to explain a number of common features in the data including shoulders at
intermediate angles, a uniform response over a wide angular range and the
greater discrimination between individual defect populations at higher fields.
We also correct several misconceptions including the idea that a peak in the
angular dependence of the critical current is a necessary signature of strong
correlated pinning, and conversely that the existence of such a peak implies
the existence of correlated pinning aligned to the particular direction. The
consistency of the vortex path model with the principle of maximum entropy is
introduced.Comment: 14 pages, 7 figure
On possibility of Decoherence due to Relativistic Effect
This note looks at the possibility of a system of free particles presenting
decoherence in the total momentum when tracing upon their relative momenta if
we take into account a relativistic correction to the expression of the kinetic
energy.Comment: 16 pages, Latex, no figure
Decoherence from internal degrees of freedom for cluster of mesoparticles : a hierarchy of master equations
A mesoscopic evolution equation for an ensemble of mesoparticles follows
after the elimination of internal degrees of freedom. If the system is composed
of a hierarchy of scales, the reduction procedure could be worked repeatedly
and the characterization of this iterating method is carried out. Namely, a
prescription describing a discrete hierarchy of master equations for the
density operator is obtained. Decoherence follows from the irreversible
coupling of the systems, defined by mesoscopic variables, to internal degrees
of freedom. We discuss briefly the existence of systems with the same dynamics
laws at different scales. We made an explicit calculation for an ensemble of
particles with internal harmonic interaction in an external anharmonic field.
New conditions related to the semiclassical limit for mesoscopic systems
(Wigner-function) are conjectured.Comment: 19 pages, 0 figures, late