15,142 research outputs found
Source conductance scaling for high frequency superconducting quasiparticle receivers
It has been suggested that the optimum source conductance G(sub s) for the superconductor-insulator-superconductor (SIS) quasiparticle mixer should have a l/f dependence. This would imply that the critical current density of SIS junctions used for mixing should increase as frequency squared, a stringent constraint on the design of submillimeter SIS mixers, rather than in simple proportion to frequency as previously believed. We have used Tucker's quantum theory of mixing for extensive numerical calculations to determine G(sub s) for an optimized SIS receiver. We find that G(sub s) is very roughly independent of frequency (except for the best junctions at low frequency), and discuss the implications of our results for the design of submillimeter SIS mixers
Hypersurfaces in Hyperbolic Poincar\'e Manifolds and Conformally Invariant PDEs
We derive a relationship between the eigenvalues of the Weyl-Schouten tensor
of a conformal representative of the conformal infinity of a hyperbolic
Poincar\'e manifold and the principal curvatures on the level sets of its
uniquely associated defining function with calculations based on [9] [10]. This
relationship generalizes the result for hypersurfaces in {\H}^{n+1} and their
connection to the conformal geometry of {\SS}^n as exhibited in [7] and gives
a correspondence between Weingarten hypersurfaces in hyperbolic Poincar\'e
manifolds and conformally invariant equations on the conformal infinity. In
particular, we generalize an equivalence exhibited in [7] between
Christoffel-type problems for hypersurfaces in {\H}^{n+1} and scalar
curvature problems on the conformal infinity {\SS}^n to hyperbolic Poincar\'e
manifolds.Comment: 16 page
The physics of large-scale food crises
Investigating the ``physics'' of food crises consists in identifying features
which are common to all large-scale food crises. One element which stands out
is the fact that during a food crisis there is not only a surge in deaths but
also a correlative temporary decline in conceptions and subsequent births. As a
matter of fact, birth reduction may even start several months before the death
surge and can therefore serve as an early warning signal of an impending
crisis. This scenario is studied in three cases of large-scale food crises.
Finland (1868), India (1867--1907), China (1960--1961). It turns out that
between the regional amplitudes of death spikes and birth troughs there is a
power law relationship. This confirms what was already observed for the
epidemic of 1918 in the United States (Richmond et al. 2018b). In a second part
of the paper we explain how this relationship can be used for the investigation
of mass-mortality episodes in cases where direct death data are either
uncertain or nonexistent.Comment: 29 pages, 11 figure
Resummation Effects in the Search of SM Higgs Boson at Hadron Colliders
We examine the soft-gluon resummation effects, including the exact spin
correlations among the final state particles, in the search of the Standard
Model Higgs boson, via the process H\to ZZH\to WW$
mode, the acceptance rates of the signal events predicted by the resummation
and NLO calculations are almost the same, but some of the predicted kinematical
distributions are quite different. Thus, to precisely determine the properties
of the Higgs boson at hadron colliders, the soft-gluon resummation effects have
to be taken into account.Comment: The version to appear in PR
Spin-Current-Induced Charge Accumulation and Electric Current in Semiconductor Nanostructures with Rashba Spin-Orbit Coupling
We demonstrate that the flow of a longitudinal spin current with different
spin polarization will induce different patterns of charge accumulation in a
two-terminal strip, or electric current distribution in a four-terminal
Hall-bar structure, of two-dimensional electron gas with Rashba spin-orbit
coupling (RSOC). For an in-plane polarized spin current, charges will
accumulate either by the two lateral edges or around the center of the strip
structure while, for an out-of-plain polarized spin current, charge densities
will show opposite signs by the two lateral edges leading to a Hall voltage.
Our calculation offers a new route to experimentally detect or differentiate
pure spin currents with various spin polarization.Comment: 4 pages, 3 figure
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