5,598 research outputs found
Semiparametric inference for the recurrent event process by means of a single-index model
In this paper, we introduce new parametric and semiparametric regression
techniques for a recurrent event process subject to random right censoring. We
develop models for the cumula- tive mean function and provide asymptotically
normal estimators. Our semiparametric model which relies on a single-index
assumption can be seen as a dimension reduction technique that, contrary to a
fully nonparametric approach, is not stroke by the curse of dimensional- ity
when the number of covariates is high. We discuss data-driven techniques to
choose the parameters involved in the estimation procedures and provide a
simulation study to support our theoretical results
Single-index copulae
We introduce so-called "single-index copulae". They are semi-parametric
conditional copulae whose parameter is an unknown "link" function of a
univariate index only. We provide estimates of this link function and of the
finite dimensional unknown parameter. The asymptotic properties of the latter
estimates are stated. Thanks to some properties of conditional Kendall's tau,
we illustrate our technical conditions with several usual copula families.Comment: Revised version: correction of Assumption 3 and some minor induced
modification
Bimodalities : a survey of experimental data and models
Bimodal distributions of some chosen variables measured in nuclear collisions
were recently proposed as a non ambiguous signature of a first order phase
transition in nuclei. This section presents a compilation of both theoretical
and experimental studies on bimodalities performed so far, in relation with the
liquid-gas phase transition in nuclear matter.Comment: 12 pages, 18 figures, 1 table Appeared in European Physics Journal A
as part of the Topical Volume "Dynamics and Thermodynamics with Nuclear
Degrees of Freedom
Isospin effects in the thermodynamics of finite nuclei
It has been proposed that multifragmentation can be related to the liquid-gas
phase transition of nuclear matter. We study the statistical properties of
finite nuclear matter near the phase transition with the help of a Lattice Gas
Model (LGM). The original version of LGM with only one type of charge-neutral
particles is well known to feature the properties of the liquid-gas phase
transition. In this contribution, we address the effect of Coulomb and isospin
dependence interaction for the finite nuclei transition, and study the symmetry
energy properties of finite temperature systems.Comment: Proceeding of the International Workshop on Multifragmentation and
related topics, November 2007 4-7th, Caen Franc
Single index regression models in the presence of censoring depending on the covariates
Consider a random vector (X',Y)', where X is d-dimensional and Y is
one-dimensional. We assume that Y is subject to random right censoring. The aim
of this paper is twofold. First, we propose a new estimator of the joint
distribution of (X',Y)'. This estimator overcomes the common
curse-of-dimensionality problem, by using a new dimension reduction technique.
Second, we assume that the relation between X and Y is given by a mean
regression single index model, and propose a new estimator of the parameters in
this model. The asymptotic properties of all proposed estimators are obtained.Comment: Published in at http://dx.doi.org/10.3150/12-BEJ464 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
Absolute frequency measurements for hyperfine structure determination of the R(26) 62-0 transition at 501.7 nm in molecular iodine
The absolute frequencies of the hyperfine components of the R(26) 62-0
transition in molecular iodine at 501.7 nm are measured for the first time with
an optical clockwork based on a femtosecond laser frequency comb generator. The
set-up is composed of an Ar+ laser locked to a hyperfine component of the R(26)
62-0 transition detected in a continuously pumped low-pressure cell (0.33 Pa).
The detected resonances show a linewidth of 45 kHz (half-width at
half-maximum). The uncertainty of the frequency measurement is estimated to be
250 Hz
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