13,201 research outputs found
Rejoinder: Harold Jeffreys's Theory of Probability Revisited
We are grateful to all discussants of our re-visitation for their strong
support in our enterprise and for their overall agreement with our perspective.
Further discussions with them and other leading statisticians showed that the
legacy of Theory of Probability is alive and lasting. [arXiv:0804.3173]Comment: Published in at http://dx.doi.org/10.1214/09-STS284REJ the
Statistical Science (http://www.imstat.org/sts/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Quantum phases of mixtures of atoms and molecules on optical lattices
We investigate the phase diagram of a two-species Bose-Hubbard model
including a conversion term, by which two particles from the first species can
be converted into one particle of the second species, and vice-versa. The model
can be related to ultra-cold atom experiments in which a Feshbach resonance
produces long-lived bound states viewed as diatomic molecules. The model is
solved exactly by means of Quantum Monte Carlo simulations. We show than an
"inversion of population" occurs, depending on the parameters, where the second
species becomes more numerous than the first species. The model also exhibits
an exotic incompressible "Super-Mott" phase where the particles from both
species can flow with signs of superfluidity, but without global supercurrent.
We present two phase diagrams, one in the (chemical potential, conversion)
plane, the other in the (chemical potential, detuning) plane.Comment: 7 pages, 10 figure
Feshbach-Einstein condensates
We investigate the phase diagram of a two-species Bose-Hubbard model
describing atoms and molecules on a lattice, interacting via a Feshbach
resonance. We identify a region where the system exhibits an exotic super-Mott
phase and regions with phases characterized by atomic and/or molecular
condensates. Our approach is based on a recently developed exact quantum Monte
Carlo algorithm: the Stochastic Green Function algorithm with tunable
directionality. We confirm some of the results predicted by mean-field studies,
but we also find disagreement with these studies. In particular, we find a
phase with an atomic but no molecular condensate, which is missing in all
mean-field phase diagrams.Comment: 4 pages, 6 figure
Testing hypotheses via a mixture estimation model
We consider a novel paradigm for Bayesian testing of hypotheses and Bayesian
model comparison. Our alternative to the traditional construction of posterior
probabilities that a given hypothesis is true or that the data originates from
a specific model is to consider the models under comparison as components of a
mixture model. We therefore replace the original testing problem with an
estimation one that focus on the probability weight of a given model within a
mixture model. We analyze the sensitivity on the resulting posterior
distribution on the weights of various prior modeling on the weights. We stress
that a major appeal in using this novel perspective is that generic improper
priors are acceptable, while not putting convergence in jeopardy. Among other
features, this allows for a resolution of the Lindley-Jeffreys paradox. When
using a reference Beta B(a,a) prior on the mixture weights, we note that the
sensitivity of the posterior estimations of the weights to the choice of a
vanishes with the sample size increasing and avocate the default choice a=0.5,
derived from Rousseau and Mengersen (2011). Another feature of this easily
implemented alternative to the classical Bayesian solution is that the speeds
of convergence of the posterior mean of the weight and of the corresponding
posterior probability are quite similar.Comment: 25 pages, 6 figures, 2 table
Compressive Pattern Matching on Multispectral Data
We introduce a new constrained minimization problem that performs template
and pattern detection on a multispectral image in a compressive sensing
context. We use an original minimization problem from Guo and Osher that uses
minimization techniques to perform template detection in a multispectral
image. We first adapt this minimization problem to work with compressive
sensing data. Then we extend it to perform pattern detection using a formal
transform called the spectralization along a pattern. That extension brings out
the problem of measurement reconstruction. We introduce shifted measurements
that allow us to reconstruct all the measurement with a small overhead and we
give an optimality constraint for simple patterns. We present numerical results
showing the performances of the original minimization problem and the
compressed ones with different measurement rates and applied on remotely sensed
data.Comment: Published in IEEE Transactions on Geoscience and Remote Sensin
Development of a 75-watt 60-GHz traveling-wave tube for intersatellite communications
This program covers the initial design and development of a 75 watt, 60 GHz traveling-wave tube for intersatellite communications. The objective frequency band was 59 to 64 GHz, with a minimum tube gain of 35 dB. The objective overall efficiency at saturation was 40 percent. The tube, designated the 961H, used a coupled-cavity interaction circuit with periodic permanent magnet beam focusing to minimize the weight. For efficiency enhancement, it incorporated a four-stage depressed collector capable of radiation cooling in space. The electron gun had a low-temperature (type-M) cathode and an isolated anode. Two tubes were built and tested; one feasibility model with a single-stage collector and one experimental model that incorporated the multistage collector
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