15,551 research outputs found
Decoherence induced continuous pointer states
We investigate the reduced dynamics in the Markovian approximation of an
infinite quantum spin system linearly coupled to a phonon field at positive
temperature. The achieved diagonalization leads to a selection of the
continuous family of pointer states corresponding to a configuration space of
the one-dimensional Ising model. Such a family provides a mathematical
description of an apparatus with continuous readings.Comment: 8 page
Remote estimation of soil moisture
Two methods under consideration for making remote estimates of soil moisture involve measurements made in electromagnetic spectral region of 0.4 to 14.0 micrometers: (1) spectral reflectance, (2) soil temperature
Nonnegative Feynman-Kac Kernels in Schr\"{o}dinger's Interpolation Problem
The existing formulations of the Schr\"{o}dinger interpolating dynamics,
which is constrained by the prescribed input-output statistics data, utilize
strictly positive Feynman-Kac kernels. This implies that the related Markov
diffusion processes admit vanishing probability densities only at the
boundaries of the spatial volume confining the process. We extend the framework
to encompass singular potentials and associated nonnegative Feynman-Kac-type
kernels. It allows to deal with general nonnegative solutions of the
Schr\"{o}dinger boundary data problem. The resulting stochastic processes are
capable of both developing and destroying nodes (zeros) of probability
densities in the course of their evolution.Comment: Latex file, 25 p
Constraining from X-ray properties of Clusters of Galaxies at high redshift
Properties of high redshift clusters are a fundamental source of information
for cosmology. It has been shown by Oukbir and Blanchard (1997) that the
combined knowledge of the redshift distribution of X-ray clusters of galaxies
and the luminosity-temperature correlation, , provides a powerful test
of the mean density of the Universe. In this paper, we address the question of
the possible evolution of this relation from an observational point of view and
its cosmological significance. We introduce a new indicator in order to measure
the evolution of the X-ray luminosity-temperature relation with redshift and
take advantage of the recent availability of temperature information for a
significant number of high and intermediate redshift X-ray clusters of
galaxies. From our analysis, we find a slightly positive evolution in the
relation. This implies a high value of the density parameter of
. However, because the selection of clusters included inour sample
is unknown, this can be considered only as a tentative result. A
well-controlled X-ray selected survey would provide a more robust answer. XMM
will be ideal for such a program.Comment: 10 pages, LaTeX, 4 figures,5 tables, accepted by A&
Use of visible, near-infrared, and thermal infrared remote sensing to study soil moisture
Two methods are described which are used to estimate soil moisture remotely using the 0.4- to 14.0 micron wavelength region: (1) measurement of spectral reflectance, and (2) measurement of soil temperature. The reflectance method is based on observations which show that directional reflectance decreases as soil moisture increases for a given material. The soil temperature method is based on observations which show that differences between daytime and nighttime soil temperatures decrease as moisture content increases for a given material. In some circumstances, separate reflectance or temperature measurements yield ambiguous data, in which case these two methods may be combined to obtain a valid soil moisture determination. In this combined approach, reflectance is used to estimate low moisture levels; and thermal inertia (or thermal diffusivity) is used to estimate higher levels. The reflectance method appears promising for surface estimates of soil moisture, whereas the temperature method appears promising for estimates of near-subsurface (0 to 10 cm)
A Way Out of the Quantum Trap
We review Event Enhanced Quantum Theory (EEQT). In Section 1 we address the
question "Is Quantum Theory the Last Word". In particular we respond to some of
recent challenging staments of H.P. Stapp. We also discuss a possible future of
the quantum paradigm - see also Section 5. In Section 2 we give a short sketch
of EEQT. Examples are given in Section 3. Section 3.3 discusses a completely
new phenomenon - chaos and fractal-like phenomena caused by a simultaneous
"measurement" of several non-commuting observables (we include picture of
Barnsley's IFS on unit sphere of a Hilbert space). In Section 4 we answer
"Frequently Asked Questions" concerning EEQT.Comment: Replacement. Corrected affiliation. Latex, one .jpg figure. To appear
in Proc. Conf. Relativistic Quantum Measurements, Napoli 1998, Ed. F.
Petruccion
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