520 research outputs found
Quantum correlations and classical resonances in an open chaotic system
We show that the autocorrelation of quantum spectra of an open chaotic system
is well described by the classical Ruelle-Pollicott resonances of the
associated chaotic strange repeller. This correspondence is demonstrated
utilizing microwave experiments on 2-D n-disk billiard geometries, by
determination of the wave-vector autocorrelation C(\kappa) from the
experimental quantum spectra S_{21}(k). The correspondence is also established
via "numerical experiments" that simulate S_{21}(k) and C(\kappa) using
periodic orbit calculations of the quantum and classical resonances.
Semiclassical arguments that relate quantum and classical correlation functions
in terms of fluctuations of the density of states and correlations of particle
density are also examined and support the experimental results. The results
establish a correspondence between quantum spectral correlations and classical
decay modes in an open systems.Comment: 10 pages, 5 eps figures, "Quantum chaos Y2K" Nobel symposium, to
appear in Physica Script
Close-packed dimers on nonorientable surfaces
The problem of enumerating dimers on an M x N net embedded on non-orientable
surfaces is considered. We solve both the Moebius strip and Klein bottle
problems for all M and N with the aid of imaginary dimer weights. The use of
imaginary weights simplifies the analysis, and as a result we obtain new
compact solutions in the form of double products. The compact expressions also
permit us to establish a general reciprocity theorem.Comment: 13 pages, 1 figure, typo corrected to the version published in Phys.
Lett. A 293, 235 (2002
North American pinewood nematode disease in China
The pinewood nematode (Bursaphelenchus xylophilus) is an important alien
invasive species in China. This pinewood nematode poses a serious threat to Chinese
forests. It does have an important impact on forestry, including economic,
environmental, ecological and social. Here, I summarize the current situation of the
occurrence and development of North American pinewood nematode disease, and
combine Chinese practices in pinewood nematode control to propose considerations
from five aspects: 1) laws, 2) national department, 3) scientific research, 4)
technology promotion and application, and 5) Science popularization and public
education, but also in terms of scientific and technological support, technology
promotion and application, scientific popularization, and public education to consider
the management strategy of pinewood nematode disease in China
Revealing the cosmic web dependent halo bias
Halo bias is the one of the key ingredients of the halo models. It was shown
at a given redshift to be only dependent, to the first order, on the halo mass.
In this study, four types of cosmic web environments: clusters, filaments,
sheets and voids are defined within a state of the art high resolution -body
simulation. Within those environments, we use both halo-dark matter
cross-correlation and halo-halo auto correlation functions to probe the
clustering properties of halos. The nature of the halo bias differs strongly
among the four different cosmic web environments we describe. With respect to
the overall population, halos in clusters have significantly lower biases in
the {} mass range. In other
environments however, halos show extremely enhanced biases up to a factor 10 in
voids for halos of mass {}. Such a strong
cosmic web environment dependence in the halo bias may play an important role
in future cosmological and galaxy formation studies. Within this cosmic web
framework, the age dependency of halo bias is found to be only significant in
clusters and filaments for relatively small halos \la 10^{12.5}\msunh.Comment: 14 pages, 14 figures, ApJ accepte
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