68 research outputs found
Identifying wave packet fractional revivals by means of information entropy
Wave packet fractional revivals is a relevant feature in the long time scale
evolution of a wide range of physical systems, including atoms, molecules and
nonlinear systems. We show that the sum of information entropies in both
position and momentum conjugate spaces is an indicator of fractional revivals
by analyzing three different model systems: the infinite square well,
a particle bouncing vertically against a wall in a gravitational field,
and the vibrational dynamics of hydrogen iodide molecules. This
description in terms of information entropies complements the usual one in
terms of the autocorrelation function
Analytic results for Gaussian wave packets in four model systems: II. Autocorrelation functions
The autocorrelation function, A(t), measures the overlap (in Hilbert space)
of a time-dependent quantum mechanical wave function, psi(x,t), with its
initial value, psi(x,0). It finds extensive use in the theoretical analysis and
experimental measurement of such phenomena as quantum wave packet revivals. We
evaluate explicit expressions for the autocorrelation function for
time-dependent Gaussian solutions of the Schrodinger equation corresponding to
the cases of a free particle, a particle undergoing uniform acceleration, a
particle in a harmonic oscillator potential, and a system corresponding to an
unstable equilibrium (the so-called `inverted' oscillator.) We emphasize the
importance of momentum-space methods where such calculations are often more
straightforwardly realized, as well as stressing their role in providing
complementary information to results obtained using position-space
wavefunctions.Comment: 18 pages, RevTeX, to appear in Found. Phys. Lett, Vol. 17, Dec. 200
Quantum Supearrivals
A curious effect is uncovered by calculating the it time evolving probability
of reflection of a Gaussian wave packet from a rectangular potential barrier
while it is perturbed by reducing its height. A time interval is found during
which this probability of reflection is larger (``superarrivals'') than in the
unperturbed case. This nonclassical effect can be explained by requiring a wave
function to act as a ``field'' through which an action, induced by the
perturbation of the boundary condition, propagates at a speed depending upon
the rate of reducing the barrier height.Comment: 4 new .eps figures added. Majour changes include explanation of
superarrivals through dynamical effect induced by perturbing barrie
Superrevivals in the quantum dynamics of a particle confined in a finite square well potential
We examine the revival features in wave packet dynamics of a particle
confined in a finite square well potential. The possibility of tunneling
modifies the revival pattern as compared to an infinite square well potential.
We study the dependence of the revival times on the depth of the square well
and predict the existence of superrevivals. The nature of these superrevivals
is compared with similar features seen in the dynamics of wavepackets in an
anharmonic oscillator potential.Comment: 8 pages in Latex two-column format with 5 figures (eps). To appear in
Physical Review
Phase and Pupil Amplitude Recovery for JWST Space-Optics Control
This slide presentation reviews the phase and pupil amplitude recovery for the James Webb Space Telescope (JWST) Near Infrared Camera (NIRCam). It includes views of the Integrated Science Instrument Module (ISIM), the NIRCam, examples of Phase Retrieval Data, Ghost Irradiance, Pupil Amplitude Estimation, Amplitude Retrieval, Initial Plate Scale Estimation using the Modulation Transfer Function (MTF), Pupil Amplitude Estimation vs lambda, Pupil Amplitude Estimation vs. number of Images, Pupil Amplitude Estimation vs Rotation (clocking), and Typical Phase Retrieval Results Also included is information about the phase retrieval approach, Non-Linear Optimization (NLO) Optimized Diversity Functions, and Least Square Error vs. Starting Pupil Amplitude
Quantum Revivals in Periodically Driven Systems close to nonlinear resonance
We calculate the quantum revival time for a wave-packet initially well
localized in a one-dimensional potential in the presence of an external
periodic modulating field. The dependence of the revival time on various
parameters of the driven system is shown analytically. As an example of
application of our approach, we compare the analytically obtained values of the
revival time for various modulation strengths with the numerically computed
ones in the case of a driven gravitational cavity. We show that they are in
very good agreement.Comment: 14 pages, 1 figur
Decoherence of molecular wave packets in an anharmonic potential
The time evolution of anharmonic molecular wave packets is investigated under
the influence of the environment consisting of harmonic oscillators. These
oscillators represent photon or phonon modes and assumed to be in thermal
equilibrium. Our model explicitly incorporates the fact that in the case of a
nonequidistant spectrum the rates of the environment induced transitions are
different for each transition. The nonunitary time evolution is visualized by
the aid of the Wigner function related to the vibrational state of the
molecule. The time scale of decoherence is much shorter than that of
dissipation, and gives rise to states which are mixtures of localized states
along the phase space orbit of the corresponding classical particle. This
behavior is to a large extent independent of the coupling strength, the
temperature of the environment and also of the initial state.Comment: 7 pages, 4 figure
Immune pathways and defence mechanisms in honey bees Apis mellifera
Social insects are able to mount both group-level and individual defences against pathogens. Here we focus on individual defences, by presenting a genome-wide analysis of immunity in a social insect, the honey bee Apis mellifera. We present honey bee models for each of four signalling pathways associated with immunity, identifying plausible orthologues for nearly all predicted pathway members. When compared to the sequenced Drosophila and Anopheles genomes, honey bees possess roughly one-third as many genes in 17 gene families implicated in insect immunity. We suggest that an implied reduction in immune flexibility in bees reflects either the strength of social barriers to disease, or a tendency for bees to be attacked by a limited set of highly coevolved pathogens
Temporal Analysis of the Honey Bee Microbiome Reveals Four Novel Viruses and Seasonal Prevalence of Known Viruses, Nosema, and Crithidia
Honey bees (Apis mellifera) play a critical role in global food production as pollinators of numerous crops. Recently, honey bee populations in the United States, Canada, and Europe have suffered an unexplained increase in annual losses due to a phenomenon known as Colony Collapse Disorder (CCD). Epidemiological analysis of CCD is confounded by a relative dearth of bee pathogen field studies. To identify what constitutes an abnormal pathophysiological condition in a honey bee colony, it is critical to have characterized the spectrum of exogenous infectious agents in healthy hives over time. We conducted a prospective study of a large scale migratory bee keeping operation using high-frequency sampling paired with comprehensive molecular detection methods, including a custom microarray, qPCR, and ultra deep sequencing. We established seasonal incidence and abundance of known viruses, Nosema sp., Crithidia mellificae, and bacteria. Ultra deep sequence analysis further identified four novel RNA viruses, two of which were the most abundant observed components of the honey bee microbiome (∼1011 viruses per honey bee). Our results demonstrate episodic viral incidence and distinct pathogen patterns between summer and winter time-points. Peak infection of common honey bee viruses and Nosema occurred in the summer, whereas levels of the trypanosomatid Crithidia mellificae and Lake Sinai virus 2, a novel virus, peaked in January
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