1,156 research outputs found
Non-archimedean Yomdin-Gromov parametrizations and points of bounded height
We prove an analogue of the Yomdin-Gromov Lemma for -adic definable sets
and more broadly in a non-archimedean, definable context. This analogue keeps
track of piecewise approximation by Taylor polynomials, a nontrivial aspect in
the totally disconnected case. We apply this result to bound the number of
rational points of bounded height on the transcendental part of -adic
subanalytic sets, and to bound the dimension of the set of complex polynomials
of bounded degree lying on an algebraic variety defined over , in analogy to results by Pila and Wilkie, resp. by Bombieri and Pila.
Along the way we prove, for definable functions in a general context of
non-archimedean geometry, that local Lipschitz continuity implies piecewise
global Lipschitz continuity.Comment: 54 pages; revised, section 5.6 adde
The Marseille Schmidt survey for active star-forming galaxies. I. Data on 92 emission line objects in two fields
We present data from a moderately deep spectroscopic Schmidt survey
(Blim=17.5) of ``active galaxies'' selected by the presence of emission lines
in their spectra and/or their UV excess. The redshift, magnitudes, color and
diameter reduction methods have been discussed in a previous paper. Here we
explain the emission line equivalent width determination method. 92 emission
line objects have been found in two adjacent fields (approximately 50deg^2) in
the direction of the south extension of the Virgo cluster. We give a catalog
containing positions, photographic R and B magnitudes, U-R colors, effective
diameters, redshifts, equivalent widths and intensity ratios of the
[OIII]4959,5007, Hbeta and [OII] 3727 emission lines. On these fields, we
evaluate the completeness limit of the survey at a pseudo B magnitude value of
15.7.Comment: tar gzipped file 7 AA latex2e pages(including 7 figures) + 1 tex
table (2 pages) + 5 pages (color ps) charts will appear in A&A, available
also at http://hasso.mpia-hd.mpg.de/Surace/surace.html#article
Adaptive estimation of the hazard rate with multiplicative censoring
We propose an adaptive estimation procedure of the hazard rate of a random variable X in the multiplicative censoring model, Y = XU , with U ∼ U([0, 1]) independent of X. The variable X is not directly observed: an estimator is built from a sample {Y1, ..., Yn} of copies of Y. It is obtained by minimisation of a contrast function over a class of general nested function spaces which can be generated e.g. by splines functions. The dimension of the space is selected by a penalised contrast criterion. The final estimator is proved to achieve the best bias-variance compromise and to reach the same convergence rate as the oracle estimator under conditions on the maximal dimension. The good behavior of the resulting estimator is illustrated over a simulation study
Fluctuations in the Irreversible Decay of Turbulent Energy
A fluctuation law of the energy in freely-decaying, homogeneous and isotropic
turbulence is derived within standard closure hypotheses for 3D incompressible
flow. In particular, a fluctuation-dissipation relation is derived which
relates the strength of a stochastic backscatter term in the energy decay
equation to the mean of the energy dissipation rate. The theory is based on the
so-called ``effective action'' of the energy history and illustrates a
Rayleigh-Ritz method recently developed to evaluate the effective action
approximately within probability density-function (PDF) closures. These
effective actions generalize the Onsager-Machlup action of nonequilibrium
statistical mechanics to turbulent flow. They yield detailed, concrete
predictions for fluctuations, such as multi-time correlation functions of
arbitrary order, which cannot be obtained by direct PDF methods. They also
characterize the mean histories by a variational principle.Comment: 26 pages, Latex Version 2.09, plus seceq.sty, a stylefile for
sequential numbering of equations by section. This version includes new
discussion of the physical interpretation of the formal Rayleigh-Ritz
approximation. The title is also change
The Crab pulsar light curve in the soft gamma ray range: FIGARO II results
The FIGARO II experiment (a large area, balloon borne, crystal scintillator detector working from 0.15 to 4.3 MeV) observed the Crab pulsar on 1990 Jul. 9 for about seven hours. The study of the pulse profile confirms some structures detected with a low significance during the shorter observation of 1986, and adds new important elements to the picture. In particular, between the two main peaks, two secondary peaks appear centered at phase values 0.1 and 0.3, in the energy range 0.38 to 0.49 MeV; in the same energy range, a spectral feature at 0.44 MeV, interpreted as a redshifted positron annihilation line, was observed during the same balloon flight in the phase interval including the second main peak and the neighboring secondary peak. If the phase interval considered is extended to include also the other secondary peak, the significance of the spectral line appears to increase
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