35,497 research outputs found
Cryogenic-coolant He4-superconductor dynamic and static interactions
A composite superconducting material (NbTi-Cu) was evaluated with emphasis on post quench solid cooling interaction regimes. The quasi-steady runs confirm the existence of a thermodynamic limiting thickness for insulating coatings. Two distinctly different post quench regimes of coated composites are shown to relate to the limiting thickness. Only one regime,, from quench onset to the peak value, revealed favorable coolant states, in particular in He2. Transient recovery shows favorable recovery times from this post quench regime (not drastically different from bare conductors) for both single coated specimens and a coated conductor bundle
Temperature dependence of spatially heterogeneous dynamics in a model of viscous silica
Molecular dynamics simulations are performed to study spatially heterogeneous
dynamics in a model of viscous silica above and below the critical temperature
of the mode coupling theory, . Specifically, we follow the evolution
of the dynamic heterogeneity as the temperature dependence of the transport
coefficients shows a crossover from non-Arrhenius to Arrhenius behavior when
the melt is cooled. It is demonstrated that, on intermediate time scales, a
small fraction of oxygen and silicon atoms are more mobile than expected from a
Gaussian approximation. These highly mobile particles form transient clusters
larger than that resulting from random statistics, indicating that dynamics are
spatially heterogeneous. An analysis of the clusters reveals that the mean
cluster size is maximum at times intermediate between ballistic and diffusive
motion, and the maximum size increases with decreasing temperature. In
particular, the growth of the clusters continues when the transport
coefficients follow an Arrhenius law. These findings imply that the structural
relaxation in silica cannot be understood as a statistical bond breaking
process. Though the mean cluster sizes for silica are at the lower end of the
spectrum of values reported in the literature, we find that spatially
heterogeneous dynamics in strong and fragile glass formers are similar on a
qualitative level. However, different from results for fragile liquids, we show
that correlated particle motion along quasi one-dimensional, string-like paths
is of little importance for the structural relaxation in this model of silica,
suggesting that string-like motion is suppressed by the presence of covalent
bonds.Comment: 13 pages, 11 figure
Plasmon assisted transmission of high dimensional orbital angular momentum entangled state
We present an experimental evidence that high dimensional orbital angular
momentum entanglement of a pair of photons can be survived after a
photon-plasmon-photon conversion. The information of spatial modes can be
coherently transmitted by surface plasmons. This experiment primarily studies
the high dimensional entangled systems based on surface plasmon with
subwavelength structures. It maybe useful in the investigation of spatial mode
properties of surface plasmon assisted transmission through subwavelength hole
arrays.Comment: 7 pages,6 figure
Retrieving qubit information despite decoherence
The time evolution of a qubit, consisting of two single-level quantum dots,
is studied in the presence of telegraph noise. The dots are connected by two
tunneling paths, with an Aharonov-Bohm flux enclosed between them. Under
special symmetry conditions, which can be achieved by tuning gate voltages,
there develops partial decoherence: at long times, the off-diagonal element of
the reduced density matrix (in the basis of the two dot states) approaches a
non-zero value, generating a circulating current around the loop. The flux
dependence of this current contains full information on the initial quantum
state of the qubit, even at infinite time. Small deviations from this symmetry
yield a very slow exponential decay towards the fully-decoherent limit.
However, the amplitudes of this decay also contain the full information on the
initial qubit state, measurable either via the current or via the occupations
of the qubit dots.Comment: 10 pages, 4 figure
Theory and simulation of the nematic zenithal anchoring coefficient
Combining molecular simulation, Onsager theory and the elastic description of
nematic liquid crystals, we study the dependence of the nematic liquid crystal
elastic constants and the zenithal surface anchoring coefficient on the value
of the bulk order parameter
Resonant growth of stellar oscillations by incident gravitational waves
Stellar oscillation under the combined influences of incident gravitational
wave and radiation loss is studied in a simple toy model. The star is
approximated as a uniform density ellipsoid in the Newtonian gravity including
radiation damping through quadrupole formula. The time evolution of the
oscillation is significantly controlled by the incident wave amplitude ,
frequency and damping time . If a combination
exceeds a threshold value, which depends on the resonance mode, the resonant
growth is realized.Comment: 11 pages, 6 figures, Accepted for the publication in Classical and
Quantum Gravit
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