4,626 research outputs found
Riemann-Liouville processes arising from Branching particle systems
It is proved in this paper that Riemann-Liouville processes can arise from
the temporal structures of the scaled occupation time fluctuation limits of the
site-dependent (d,\alpha,\sigma(x))branching particle systems in the case of
1=d<\alpha<2 and \int_{\R}\sigma(x)\d x<\infty.Comment: 12 page
On the moment limit of quantum observables, with an application to the balanced homodyne detection
We consider the moment operators of the observable (i.e. a semispectral
measure or POM) associated with the balanced homodyne detection statistics,
with paying attention to the correct domains of these unbounded operators. We
show that the high amplitude limit, when performed on the moment operators,
actually determines uniquely the entire statistics of a rotated quadrature
amplitude of the signal field, thereby verifying the usual assumption that the
homodyne detection achieves a measurement of that observable. We also consider,
in a general setting, the possibility of constructing a measurement of a single
quantum observable from a sequence of observables by taking the limit on the
level of moment operators of these observables. In this context, we show that
under some natural conditions (each of which is satisfied by the homodyne
detector example), the existence of the moment limits ensures that the
underlying probability measures converge weakly to the probability measure of
the limiting observable. The moment approach naturally requires that the
observables be determined by their moment operator sequences (which does not
automatically happen), and it turns out, in particular, that this is the case
for the balanced homodyne detector.Comment: 22 pages, no figure
Quiescence: a mechanism for escaping the effects of drug on cell populations
We point out that a simple and generic strategy to lower the risk for
extinction consists in the developing a dormant stage in which the organism is
unable to multiply but may die. The dormant organism is protected against the
poisonous environment. The result is to increase the survival probability of
the entire population by introducing a type of zero reproductive fitness. This
is possible, because the reservoir of dormant individuals act as a buffer that
can cushion fatal fluctuations in the number of births and deaths which without
the dormant population would have driven the entire population to extinction.Comment: 18 pages and 9 figure
Adaptive Transmission Techniques for Mobile Satellite Links
Adapting the transmission rate in an LMS channel is a challenging task
because of the relatively fast time variations, of the long delays involved,
and of the difficulty in mapping the parameters of a time-varying channel into
communication performance. In this paper, we propose two strategies for dealing
with these impairments, namely, multi-layer coding (MLC) in the forward link,
and open-loop adaptation in the return link. Both strategies rely on
physical-layer abstraction tools for predicting the link performance. We will
show that, in both cases, it is possible to increase the average spectral
efficiency while at the same time keeping the outage probability under a given
threshold. To do so, the forward link strategy will rely on introducing some
latency in the data stream by using retransmissions. The return link, on the
other hand, will rely on a statistical characterization of a physical-layer
abstraction measure.Comment: Presented at the 30th AIAA International Communications Satellite
Systems Conference (ICSSC), Ottawa, Canada, 2012. Best Professional Paper
Awar
Motion in a Random Force Field
We consider the motion of a particle in a random isotropic force field.
Assuming that the force field arises from a Poisson field in , , and the initial velocity of the particle is sufficiently large, we
describe the asymptotic behavior of the particle
Atmospheric and Oceanographic Information Processing System (AOIPS) system description
The development of hardware and software for an interactive, minicomputer based processing and display system for atmospheric and oceanographic information extraction and image data analysis is described. The major applications of the system are discussed as well as enhancements planned for the future
Thermalisation of Local Observables in Small Hubbard Lattices
We present a study of thermalisation of a small isolated Hubbard lattice
cluster prepared in a pure state with a well-defined energy. We examine how a
two-site subsystem of the lattice thermalises with the rest of the system as
its environment. We explore numerically the existence of thermalisation over a
range of system parameters, such as the interaction strength, system size and
the strength of the coupling between the subsystem and the rest of the lattice.
We find thermalisation over a wide range of parameters and that interactions
are crucial for efficient thermalisation of small systems. We relate this
thermalisation behaviour to the eigenstate thermalisation hypothesis and
quantify numerically the extent to which eigenstate thermalisation holds. We
also verify our numerical results theoretically with the help of previously
established results from random matrix theory for the local density of states,
particularly the finite-size scaling for the onset of thermalisation.Comment: 22 pages, 23 figure
Central limit behavior of deterministic dynamical systems
We investigate the probability density of rescaled sums of iterates of
deterministic dynamical systems, a problem relevant for many complex physical
systems consisting of dependent random variables. A Central Limit Theorem (CLT)
is only valid if the dynamical system under consideration is sufficiently
mixing. For the fully developed logistic map and a cubic map we analytically
calculate the leading-order corrections to the CLT if only a finite number of
iterates is added and rescaled, and find excellent agreement with numerical
experiments. At the critical point of period doubling accumulation, a CLT is
not valid anymore due to strong temporal correlations between the iterates.
Nevertheless, we provide numerical evidence that in this case the probability
density converges to a -Gaussian, thus leading to a power-law generalization
of the CLT. The above behavior is universal and independent of the order of the
maximum of the map considered, i.e. relevant for large classes of critical
dynamical systems.Comment: 6 pages, 5 figure
Mapping of hydrothermal alternation zones and regional rock types using computer enhanced ERTS MSS images
A combination of digital computer processing and color compositing of ERTS MSS images has been used to map hydrothermal alternation zones and regional rock types in south-central Nevada. The technique is based on enhancement of subtle visible and near infrared reflectivity differences between mineralogically dissimilar rocks, especially unaltered and altered rocks. MSS spectral bands are ratioed, pixel by pixel, in the computer and subsequently stretched. These ratio values are used to produce a new black and white image which shows the subtle spectral reflectivity differences. Additional enhancement is achieved by preparing color composites of two or more stretched ratio images. The choice of MSS bands for rationing depends on the spectral reflectance properties of the rocks to be discriminated. Although this technique is in the initial stage of development and is untested in other areas, it already appears to have considerable potential for targeting mineral prospects and for regional geologic mapping
Fluctuations of noise and the low frequency cutoff paradox
Recent experiments on blinking quantum dots and weak turbulence in liquid
crystals reveal the fundamental connection between noise and power law
intermittency. The non-stationarity of the process implies that the power
spectrum is random -- a manifestation of weak ergodicity breaking. Here we
obtain the universal distribution of the power spectrum, which can be used to
identify intermittency as the source of the noise. We solve an outstanding
paradox on the non integrability of noise and the violation of Parseval's
theorem. We explain why there is no physical low frequency cutoff and therefore
cannot be found in experiments.Comment: 5 pages, 2 figures, supplementary material (4 pages
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