13,943 research outputs found
Elliptic Flow and Shear Viscosity within a Transport Approach from RHIC to LHC Energy
We have investigated the build up of anisotropic flows within a parton
cascade approach at fixed shear viscosity to entropy density \eta/s to study
the generation of collective flows in ultra-relativistic heavy ion collisions.
We present a study of the impact of a temperature dependent \eta/s(T) on the
generation of the elliptic flow at both RHIC and LHC. Finally we show that the
transport approach, thanks to its wide validity range, is able to describe
naturally the rise - fall and saturation of the v_2(p_T) observed at LHC.Comment: 6 pages, 3 figures, proceedings of the workshop EPIC@LHC, 6-8 July
2011, Bari, Ital
Asymptotic robustness of Kelly's GLRT and Adaptive Matched Filter detector under model misspecification
A fundamental assumption underling any Hypothesis Testing (HT) problem is
that the available data follow the parametric model assumed to derive the test
statistic. Nevertheless, a perfect match between the true and the assumed data
models cannot be achieved in many practical applications. In all these cases,
it is advisable to use a robust decision test, i.e. a test whose statistic
preserves (at least asymptotically) the same probability density function (pdf)
for a suitable set of possible input data models under the null hypothesis.
Building upon the seminal work of Kent (1982), in this paper we investigate the
impact of the model mismatch in a recurring HT problem in radar signal
processing applications: testing the mean of a set of Complex Elliptically
Symmetric (CES) distributed random vectors under a possible misspecified,
Gaussian data model. In particular, by using this general misspecified
framework, a new look to two popular detectors, the Kelly's Generalized
Likelihood Ration Test (GLRT) and the Adaptive Matched Filter (AMF), is
provided and their robustness properties investigated.Comment: ISI World Statistics Congress 2017 (ISI2017), Marrakech, Morocco,
16-21 July 201
Halphen conditions and postulation of nodes
We give sharp lower bounds for the postulation of the nodes of a general
plane projection of a smooth connected curve C in P^r and we study the
relationships with the geometry of the embedding. Strict connections with
Castelnuovo's theory and Halphen's theory are shown.Comment: LaTeX, 26 page
Comment on the frozen QCD coupling
The frozen QCD coupling is a parameter often used as an effective fixed
coupling. It is supposed to mimic both the running coupling effects and the
lack of knowledge of alpha_s in the infrared region. Usually the value of the
frozen coupling is fixed from the analysis of the experimental data. We present
a novel way to define such coupling(s) independently of the experiments. We
argue that there are different frozen couplings which are used in the double-
(DL) and single- logarithmic (SL) Approximations. We introduce four kinds of
the frozen couplings: the coupling used in DLA with a time-like argument (i.e.
the coupling present in the non-singlet scattering amplitudes and DIS structure
functions) which we find 0.24 approximately; the DLA coupling with a space-like
argument (in e+e- -annihilation, in DY processes and in any scattering
amplitude in the hard or backward kinematics) which is a factor two larger,
namely 0.48. We also show that the frozen coupling in the SL evolution
equations like BFKL has to be defined in a way less accurate compared to DLA,
and our estimate for this coupling is 0.1. Our estimates for the singlet and
non-singlet intercepts are also in a good agreement with the results available
in the literature.Comment: 11 pages, 3 figure
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