1,645,760 research outputs found
Decoherence at zero temperature
Most discussions of decoherence in the literature consider the
high-temperature regime but it is also known that, in the presence of
dissipation, decoherence can occur even at zero temperature. Whereas most
previous investigations all assumed initial decoupling of the quantum system
and bath, we consider that the system and environment are entangled at all
times. Here, we discuss decoherence for a free particle in an initial
Schr\"{o}dinger cat state. Memory effects are incorporated by use of the single
relaxation time model (since the oft-used Ohmic model does not give physically
correct results)
Wiring harnesses documented by punched-card technique
Cards representing a connector are punched, sorted, and then used to printout wiring documentation for that connector. When wiring changes are made, new cards are punched and the wiring documentation is reprinted to reflect the latest configuration
Flux-Confinement in Dilatonic Cosmic Strings
We study dilaton-electrodynamics in flat spacetime and exhibit a set of
global cosmic string like solutions in which the magnetic flux is confined.
These solutions continue to exist for a small enough dilaton mass but cease to
do so above a critcal value depending on the magnetic flux. There also exist
domain wall and Dirac monopole solutions. We discuss a mechanism whereby
magnetic monopolesmight have been confined by dilaton cosmic strings during an
epoch in the early universe during which the dilaton was massless.Comment: 8 pages, DAMTP R93/3
Deformation Measurements at the Sub-Micron Size Scale: II. Refinements in the Algorithm for Digital Image Correction
Improvements are proposed in the application of the Digital Image Correlation method, a technique that compares digital images of a specimen surface before and after deformation to deduce its sureface (2-D) displacement field and strains. These refinements, tested on translations and rigid body rotations were significant with regard to the computer efficiency and covergence properties of the method. In addition, the formulation of the algorithm was extended so as to compute the three-dimensional surface displacement field from Scanning Tunneling Microscope tomographies of a deforming specimen. The reolsution of this new displacement measuring method at the namometer scale was assessed on translation and uniaxial tensile tests and was found to be 4.8 nm for in-plane displacement components and 1.5 nm for the out-of-plane one spanning a 10 x 10 ÎŒm area
A remark on kinks and time machines
We describe an elementary proof that a manifold with the topology of the
Politzer time machine does not admit a nonsingular, asymptotically flat Lorentz
metric.Comment: 4 page
On the investigations of galaxy redshift periodicity
In this article we present a historical review of study of the redshift
periodicity of galaxies, starting from the first works performed in the
seventies of the twentieth century until the present day. We discuss the
observational data and methods used, showing in which cases the discretization
of redshifts was observed. We conclude that galaxy redshift periodisation is an
effect which can really exist. We also discussed the redshift discretization in
two different structures: the Local Group of galaxies and the Hercules
Supercluster. Contrary to the previous studies we consider all galaxies which
can be regarded as a structure member disregarding the accuracy of velocity
measurements. We applied the power spectrum analysis using the Hann function
for weighting, together with the jackknife error estimator. In both the
structures we found weak effects of redshift periodisation.Comment: 10 pages, 4 figures, to be published in Part. and Nucl. Lett. 200
Short-time Dynamics of Percolation Observables
We consider the critical short-time evolution of magnetic and
droplet-percolation order parameters for the Ising model in two and three
dimensions, through Monte-Carlo simulations with the (local) heat-bath method.
We find qualitatively different dynamic behaviors for the two types of order
parameters. More precisely, we find that the percolation order parameter does
not have a power-law behavior as encountered for the magnetization, but
develops a scale (related to the relaxation time to equilibrium) in the
Monte-Carlo time. We argue that this difference is due to the difficulty in
forming large clusters at the early stages of the evolution. Our results show
that, although the descriptions in terms of magnetic and percolation order
parameters may be equivalent in the equilibrium regime, greater care must be
taken to interprete percolation observables at short times. In particular, this
concerns the attempts to describe the dynamics of the deconfinement phase
transition in QCD using cluster observables.Comment: 5 pages, 4 figure
- âŠ