1,080,224 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)
Flexible ring slosh damping baffle Patent
Flexible ring slosh damping baffle for spacecraft fuel tan
Additive for zinc electrodes
A zinc electrode for alkaline cells includes up to about ten percent by weight of Ba(OH)2.8H2O with about five percent being preferred. The zinc electrode may or may not be amalgamated with mercury
Magnetic spin excitations in diluted ferromagnetic systems: the case of
We propose a theory which allow to calculate the magnetic excitation spectrum
in diluted ferromagnetic systems. The approach is rather general and based on
the Self-Consistent local Random Phase Approximation in which disorder
(dilution) and thermal fluctuations are properly treated. To illustrate its
reliability and accuracy we calculate the magnetic excitation in the diluted
III-V magnetic semiconductor . It is shown that dilution has
a drastic effect on the excitation spectrum, indeed well defined magnon
excitations exist only in a small region of the Brillouin zone centered around
the point. We also calculate the spin stiffness in optimally annealed
sample as a function of concentration. A comparison to available
measurements is done. We find a very good agreement for both the Curie
temperature and the spin stiffness measured in well annealed samples and
provide a plausible explanation for the very small values measured in as grown
samples.Comment: The manuscript has been modified, 4 figures are included. Accepted
for publication in Eur. Phys. Let
On the Form of the Spitzer Leavitt Law and its Dependence on Metallicity
The form and metallicity-dependence of Spitzer mid-infrared Cepheid relations
are a source of debate. Consequently, Spitzer 3.6 and 4.5 um period-magnitude
and period-color diagrams were re-examined via robust routines, thus providing
the reader an alternative interpretation to consider. The relations (nearly
mean-magnitude) appear non-linear over an extensive baseline (0.45< logPo
<2.0), particularly the period-color trend, which to first-order follows
constant (3.6-4.5) color for shorter-period Cepheids and may transition into a
bluer convex trough at longer-periods. The period-magnitude functions can be
described by polynomials (e.g., [3.6 um]=Ko-(3.071+-0.059)
logPo-(0.120+-0.032)logPo^2), and Cepheid distances computed using 3.6 and 4.5
um relations agree and the latter provides a first-order consistency check (CO
sampled at 4.5 um does not seriously compromise those distances). The
period-magnitude relations appear relatively insensitive to metallicity
variations ([Fe/H]~0 to -0.75), a conclusion inferred partly from comparing
galaxy distances established from those relations and NED-D (n>700), yet a
solid conclusion awaits comprehensive mid-infrared observations for metal-poor
Cepheids in IC 1613 ([Fe/H] -1). The Cepheid-based distances were corrected for
dust obscuration using a new ratio (i.e., A(3.6)/E(B-V)=0.18+-0.06) deduced
from GLIMPSE (Spitzer) data.Comment: To appear in Ap
On approximating two distributions from a single complex-valued function
We consider the problem of approximating two, possibly unrelated probability
distributions from a single complex-valued function and its Fourier
transform. We show that this problem always has a solution within a specified
degree of accuracy, provided the distributions satisfy the necessary regularity
conditions. We describe the algorithm and construction of and provide
examples of approximating several pairs of distributions using the algorithm.Comment: 9 pages, 4 figure
Fano-Feshbach resonances in two-channel scattering around exceptional points
It is well known that in open quantum systems resonances can coalesce at an
exceptional point, where both the energies {\em and} the wave functions
coincide. In contrast to the usual behaviour of the scattering amplitude at one
resonance, the coalescence of two resonances invokes a pole of second order in
the Green's function, in addition to the usual first order pole. We show that
the interference due to the two pole terms of different order gives rise to
patterns in the scattering cross section which closely resemble Fano-Feshbach
resonances. We demonstrate this by extending previous work on the analogy of
Fano-Feshbach resonances to classical resonances in a system of two driven
coupled damped harmonic oscillators.Comment: 8 pages, 5 figures, submitted to J. Phys.
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