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 $gg\to H\to WW/ZZ \to 4 leptons, at the Tevatron and the LHC. A comparison between the resummation and the Next-to-Leading order (NLO) calculation is performed after imposing various kinematics cuts suggested in the literature for the Higgs boson search. For the$H\to ZZ$mode, the resummation effects increase the acceptance of the signal events by about 25various kinematics distributions of the final state leptons. For the$H\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