13,400 research outputs found
Brownian distance covariance
Distance correlation is a new class of multivariate dependence coefficients
applicable to random vectors of arbitrary and not necessarily equal dimension.
Distance covariance and distance correlation are analogous to product-moment
covariance and correlation, but generalize and extend these classical bivariate
measures of dependence. Distance correlation characterizes independence: it is
zero if and only if the random vectors are independent. The notion of
covariance with respect to a stochastic process is introduced, and it is shown
that population distance covariance coincides with the covariance with respect
to Brownian motion; thus, both can be called Brownian distance covariance. In
the bivariate case, Brownian covariance is the natural extension of
product-moment covariance, as we obtain Pearson product-moment covariance by
replacing the Brownian motion in the definition with identity. The
corresponding statistic has an elegantly simple computing formula. Advantages
of applying Brownian covariance and correlation vs the classical Pearson
covariance and correlation are discussed and illustrated.Comment: This paper discussed in: [arXiv:0912.3295], [arXiv:1010.0822],
[arXiv:1010.0825], [arXiv:1010.0828], [arXiv:1010.0836], [arXiv:1010.0838],
[arXiv:1010.0839]. Rejoinder at [arXiv:1010.0844]. Published in at
http://dx.doi.org/10.1214/09-AOAS312 the Annals of Applied Statistics
(http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics
(http://www.imstat.org
A spectroscopic survey of Orion KL between 41.5 and 50 GHz
Orion KL is one of the most frequently observed sources in the Galaxy, and
the site where many molecular species have been discovered for the first time.
With the availability of powerful wideband backends, it is nowadays possible to
complete spectral surveys in the entire mm-range to obtain a spectroscopically
unbiased chemical picture of the region. In this paper we present a sensitive
spectral survey of Orion KL, made with one of the 34m antennas of the Madrid
Deep Space Communications Complex in Robledo de Chavela, Spain. The spectral
range surveyed is from 41.5 to 50 GHz, with a frequency spacing of 180 kHz
(equivalent to about 1.2 km/s, depending on the exact frequency). The rms
achieved ranges from 8 to 12 mK. The spectrum is dominated by the J=1-0 SiO
maser lines and by radio recombination lines (RRLs), which were detected up to
Delta_n=11. Above a 3-sigma level, we identified 66 RRLs and 161 molecular
lines corresponding to 39 isotopologues from 20 molecules; a total of 18 lines
remain unidentified, two of them above a 5-sigma level. Results of radiative
modelling of the detected molecular lines (excluding masers) are presented. At
this frequency range, this is the most sensitive survey and also the one with
the widest band. Although some complex molecules like CH_3CH_2CN and CH_2CHCN
arise from the hot core, most of the detected molecules originate from the low
temperature components in Orion KL.Comment: Accepted for Astronomy and Astrophysics. 29 pages, 5 tables, 6
figure
Financial Forces and the Future of American Higher Education
Recent shifts in state funding are altering the most basic realities of American higher education, from student access to faculty research
The Effects of Detector Descoping and Neutral Boson Mixing on New Gauge Boson Physics at the SSC
We examine how the abilities of an SDC-like detector to discover and identify
the origin of a new neutral gauge boson are affected by mixing and
by variations in detector parameters such as lepton pair mass resolution,
particle identification efficiency, and rapidity coverage. Also examined is the
sensitivity of these results to variations in structure function uncertainties
and uncertainties in the machine integrated luminosity. Such considerations are
of importance when dealing with the issues of detector descoping and design.Comment: 17 pages, 4 figures (available by request), phyzzx, ANL-HEP-PR-92-3
Resident and Nonresident Tuition and Enrollment at Flagship State Universities
[Excerpt] How tuition levels, or the availability of grant or loan aid, influence access are empirical questions that we will not address in this chapter. Rather, we will analyze how tuition and enrollment strategies at institutions react to changes in federal and state need-based student aid and to state appropriations to public higher education institutions. The former increases student mobility by expanding their choice set, while the latter does not travel with the student
Fragmentation paths in dynamical models
We undertake a quantitative comparison of multi-fragmentation reactions, as
modeled by two different approaches: the Antisymmetrized Molecular Dynamics
(AMD) and the momentum-dependent stochastic mean-field (SMF) model. Fragment
observables and pre-equilibrium (nucleon and light cluster) emission are
analyzed, in connection to the underlying compression-expansion dynamics in
each model. Considering reactions between neutron-rich systems, observables
related to the isotopic properties of emitted particles and fragments are also
discussed, as a function of the parametrization employed for the isovector part
of the nuclear interaction. We find that the reaction path, particularly the
mechanism of fragmentation, is different in the two models and reflects on some
properties of the reaction products, including their isospin content. This
should be taken into account in the study of the density dependence of the
symmetry energy from such collisions.Comment: 11 pages, 13 figures, submitted to Phys. Rev.
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