19,950 research outputs found
Data Assimilation: A Mathematical Introduction
These notes provide a systematic mathematical treatment of the subject of
data assimilation
Loss of purity by wave packet scattering at low energies
We study the quantum entanglement produced by a head-on collision between two
gaussian wave packets in three-dimensional space. By deriving the two-particle
wave function modified by s-wave scattering amplitudes, we obtain an
approximate analytic expression of the purity of an individual particle. The
loss of purity provides an indicator of the degree of entanglement. In the case
the wave packets are narrow in momentum space, we show that the loss of purity
is solely controlled by the ratio of the scattering cross section to the
transverse area of the wave packets.Comment: 7 pages, 1 figur
S-wave quantum entanglement in a harmonic trap
We analyze the quantum entanglement between two interacting atoms trapped in
a spherical harmonic potential. At ultra-cold temperature, ground state
entanglement is generated by the dominated s-wave interaction. Based on a
regularized pseudo-potential Hamiltonian, we examine the quantum entanglement
by performing the Schmidt decomposition of low-energy eigenfunctions. We
indicate how the atoms are paired and quantify the entanglement as a function
of a modified s-wave scattering length inside the trap.Comment: 10 pages, 5 figures, to be apear in PR
Replacement of PBNA in HB and HC polymers used in SRM propellant and liner
The antioxidant phenyl-beta-naphthylamine (PBNA) was used in both HB and HC polymers. The sole (domestic) supplier of PBNA has withdrawn this product from the market, primarily because of suspected health hazards. Commercially available substitute(s) were selected and qualified for use in the two polymers
Production of photons by the parametric resonance in the dynamical Casimir effect
We calculate the number of photons produced by the parametric resonance in a
cavity with vibrating walls. We consider the case that the frequency of
vibrating wall is which is a generalization of other
works considering only , where is the fundamental-mode
frequency of the electromagnetic field in the cavity. For the calculation of
time-evolution of quantum fields, we introduce a new method which is borrowed
from the time-dependent perturbation theory of the usual quantum mechanics.
This perturbation method makes it possible to calculate the photon number for
any and to observe clearly the effect of the parametric resonance.Comment: 15 pages, RevTeX, no figure
Optimizing photon indistinguishability in the emission from incoherently-excited semiconductor quantum dots
Most optical quantum devices require deterministic single-photon emitters.
Schemes so far demonstrated in the solid state imply an energy relaxation which
tends to spoil the coherent nature of the time evolution, and with it the
photon indistinguishability. We focus our theoretical investigation on
semiconductor quantum dots embedded in microcavities. Simple and general
relations are identified between the photon indistinguishability and the
collection efficiency. The identification of the key parameters and of their
interplay provides clear indications for the device optimization
Design approaches and materials processes for ultrahigh efficiency lattice mismatched multi-junction solar cells
In this study, we report synthesis of large area
(>2cm^2), crack-free GaAs and GaInP double
heterostructures grown in a multi-junction solar cell-like
structure by MOCVD. Initial solar cell data are also
reported for GaInP top cells. These samples were grown
on Ge/Si templates fabricated using wafer bonding and ion
implantation induced layer transfer techniques. The double
heterostructures exhibit radiative emission with uniform
intensity and wavelength in regions not containing
interfacial bubble defects. The minority carrier lifetime of
~1ns was estimated from photoluminescence decay
measurements in both double heterostructures.
We also report on the structural characteristics of
heterostructures, determined via atomic force microscopy
and transmission electron microscopy, and correlate these
characteristics to the spatial variation of the minority
carrier lifetime
Nonthermal Emission from the Arches Cluster (G0.121+0.017) and the Origin of -ray Emission from 3EG J1746-2851
High resolution VLA observations of the Arches cluster near the Galactic
center show evidence of continuum emission at 3.6, 6, 20 and 90cm. The
continuum emission at 90cm is particularly striking because thermal
sources generally become optically thick at longer wavelengths and fall off in
brightness whereas non-thermal sources increase in brightness. It is argued
that the radio emission from this unique source has compact and diffuse
components produced by thermal and nonthermal processes, respectively. Compact
sources within the cluster arise from stellar winds of mass-losing stars (Lang,
Goss & Rodriguez 2001a) whereas diffuse emission is likely to be due to
colliding wind shocks of the cluster flow generating relativistic particles due
to diffuse shock acceleration. We also discuss the possibility that
-ray emission from 3EG J1746--2851, located within 3.3 of the Arches
cluster, results from the inverse Compton scattering of the radiation field of
the cluster.Comment: 15 pages, four figures, ApJL (in press
- …