0

A second quantised theory of electrons and positrons in a deep time-dependent potential well is discussed. It is shown that positron production from the well is a natural consequence of Dirac’s hole theory when the strength of the well becomes supercritical. A formalism is developed whereby the amplitude for emission of a positron of a given momentum can be calculated. The difference between po...

We have developed a quantitative theory of Cooper pair pumping in gated one-dimensional arrays of Josephson junctions. The pumping accuracy is limited by quantum tunneling of Cooper pairs out of the propagating potential well and by direct supercurrent flow through the array. Both corrections decrease exponentially with the number N of junctions in the array, but give a serious limitation of ac...

The time of protostellar wind breakout may be determined by the evolution of the infalling flow, rather than any sudden change in the central engine. I examine the transition from pure infall to outflow, in the context of the inside-out collapse of a rotating molecular cloud core. I have followed numerically the motion of the shocked shell created by the impact of a stellar wind and infalling g...

Neutrinos emitted from near the surface of the hot proto-neutron star produced by a supernova explosion may be subject to significant gravitational redshift at late times. Electron antineutrinos (ν̄e) decouple deeper in the gravitational potential well of the neutron star than do the electron neutrinos (νe), so that the ν̄e experience a larger redshift effect than do the νe. We show how this diff...

091301-1 Presented are details of the staged electron laser acceleration (STELLA) experiment, which demonstrated high-trapping efficiency and narrow energy spread in a staged laser-driven accelerator. Trapping efficiencies of up to 80% and energy spreads down to 0.36% (1 ) were demonstrated. The experiment validated an approach that may be suitable for the basic design of a laser-driven acceler...

Ears are an emergent biometric accruing application advantages including no requirement for subject contact and acquisition without demand. To recognize a subject's ear, we aim to extract a characteristic vector from a human ear image that may subsequently be used to identify or confirm the identity of the owner. Towards this end, a novel force field transformation and potential well extraction...

We use single nanoparticle luminescence microscopy to determine a distribution of individual chromophores present in porous Si nanoparticles. From these distributions, we determine the average number of emitting chromophores in each nanoparticle and the fluorescence emission count rate of a single chromophore within the porous silicon nanoparticle. We also show that the same size nanoparticles ...

We examine the hypothesis that there exists a simple scaling between the observed velocities of jets found in young stellar objects (YSOs) and jets found in active galactic nuclei (AGN). We employ a very simplified physical model of the jet acceleration process. We use timedependent, spherically symmetric wind models in Newtonian and relativistic gravitational fields to ask whether the energy i...

When the dimension of a solid structure is reduced, there will be two emerging effects, quantum confinement and surface effect, which dominate at nanoscale. Based on first-principles calculations, we demonstrate that due to an intriguing interplay between these two dominating effects, the topological and electronic (topoelectronic) properties of Sb (111) nanofilms undergo a series of transition...