9,511 research outputs found
Nanoscale quantum dot infrared sensors with photonic crystal cavity
We report high performance infrared sensors that are based on intersubband transitions in nanoscale self-assembled quantum dots combined with a microcavity resonator made with a high-index-contrast two-dimensional photonic crystal. The addition of the photonic crystal cavity increases the photocurrent, conversion efficiency, and the signal to noise ratio (represented by the specific detectivity D*) by more than an order of magnitude. The conversion efficiency of the detector at Vb=–2.6 V increased from 7.5% for the control sample to 95% in the PhC detector. In principle, these photonic crystal resonators are technology agnostic and can be directly integrated into the manufacturing of present day infrared sensors using existing lithographic tools in the fabrication facility
Extending Feynman's Formalisms for Modelling Human Joint Action Coordination
The recently developed Life-Space-Foam approach to goal-directed human action
deals with individual actor dynamics. This paper applies the model to
characterize the dynamics of co-action by two or more actors. This dynamics is
modelled by: (i) a two-term joint action (including cognitive/motivatonal
potential and kinetic energy), and (ii) its associated adaptive path integral,
representing an infinite--dimensional neural network. Its feedback adaptation
loop has been derived from Bernstein's concepts of sensory corrections loop in
human motor control and Brooks' subsumption architectures in robotics.
Potential applications of the proposed model in human--robot interaction
research are discussed.
Keywords: Psycho--physics, human joint action, path integralsComment: 6 pages, Late
Energy Dependence of the Delta Resonance: Chiral Dynamics in Action
There is an important connection between the low energy theorems of QCD and
the energy dependence of the Delta resonance in pi-N scattering, as well as the
closely related gamma^{*} N -> pi N reaction. The resonance shape is due not
only to the strong pi-N interaction in the p wave but the small interaction in
the s wave; the latter is due to spontaneous chiral symmetry breaking in QCD
(i.e. the Nambu-Goldstone nature of the pion). A brief overview of experimental
tests of chiral perturbation theory and chiral based models is presentedComment: 11 pages, 6 figures, Festschrift for S.N. yan
Quantum rainbow scattering at tunable velocities
Elastic scattering cross sections are measured for lithium atoms colliding
with rare gas atoms and SF6 molecules at tunable relative velocities down to
~50 m/s. Our scattering apparatus combines a velocity-tunable molecular beam
with a magneto-optic trap that provides an ultracold cloud of lithium atoms as
a scattering target. Comparison with theory reveals the quantum nature of the
collision dynamics in the studied regime, including both rainbows as well as
orbiting resonances
Neutrinos and Nucleosynthesis in Supernova
The type II supernova is considered as a candidate site for the production of
heavy elements. The nucleosynthesis occurs in an intense neutrino flux, we
calculate the electron fraction in this environment.Comment: RevTex4 style, 3 pages including 1 figure. Presented at Mexican
School of Astrophysics 2002, Guanajuato, Mexico, 31 Jul - 7 Aug 2002. Final
version to appear in the Proceedings of IX Mexican Workshop on Particles and
Fields Physics Beyond the Standard Model, Colima Col. Mexico, November 17-22,
200
Effect of light polarization on plasma distribution and filament formation
We show that, for 200 fs light pulses at 790 nm, the formation of filaments
is strongly affected by the laser light polarization . Filamentation does not
exist for a pure circularly polarized light, propagating in vacuum before
focusing in air, while there is no difference for focusing the light in air or
vacuum for linearly polarized light.Comment: 4pages 2 figure
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