1,650 research outputs found
Cross-section and polarization of neutrino-produced 's made simple
Practical formulae are derived for the cross-section and polarization of the
lepton produced in deep-inelastic neutrino-nucleon scattering in the
frame of the simple quark-parton model.Comment: 10 pages, no figure
Estimating the number of change-points in a two-dimensional segmentation model without penalization
In computational biology, numerous recent studies have been dedicated to the
analysis of the chromatin structure within the cell by two-dimensional
segmentation methods. Motivated by this application, we consider the problem of
retrieving the diagonal blocks in a matrix of observations. The theoretical
properties of the least-squares estimators of both the boundaries and the
number of blocks proposed by L\'evy-Leduc et al. [2014] are investigated. More
precisely, the contribution of the paper is to establish the consistency of
these estimators. A surprising consequence of our results is that, contrary to
the onedimensional case, a penalty is not needed for retrieving the true number
of diagonal blocks. Finally, the results are illustrated on synthetic data.Comment: 30 pages, 8 figure
Estimating the large-scale angular power spectrum in the presence of systematics: a case study of Sloan Digital Sky Survey quasars
The angular power spectrum is a powerful statistic for analysing cosmological
signals imprinted in the clustering of matter. However, current galaxy and
quasar surveys cover limited portions of the sky, and are contaminated by
systematics that can mimic cosmological signatures and jeopardise the
interpretation of the measured power spectra. We provide a framework for
obtaining unbiased estimates of the angular power spectra of large-scale
structure surveys at the largest scales using quadratic estimators. The method
is tested by analysing the 600 CMASS mock catalogues constructed by Manera et
al. (2013) for the Baryon Oscillation Spectroscopic Survey (BOSS). We then
consider the Richards et al. (2009) catalogue of photometric quasars from the
Sixth Data Release (DR6) of the Sloan Digital Sky Survey (SDSS), which is known
to include significant stellar contamination and systematic uncertainties.
Focusing on the sample of ultraviolet-excess (UVX) sources, we show that the
excess clustering power present on the largest-scales can be largely mitigated
by making use of improved sky masks and projecting out the modes corresponding
to the principal systematics. In particular, we find that the sample of objects
with photometric redshift exhibits no evidence of
contamination when using our most conservative mask and mode projection. This
indicates that any residual systematics are well within the statistical
uncertainties. We conclude that, using our approach, this sample can be used
for cosmological studies.Comment: 18 pages, 18 figures. Version accepted by MNRA
Sub-ballistic behavior in quantum systems with L\'evy noise
We investigate the quantum walk and the quantum kicked rotor in resonance
subjected to noise with a L\'evy waiting time distribution. We find that both
systems have a sub-ballistic wave function spreading as shown by a power-law
tail of the standard deviation.Comment: 4 pages, 4 figure
Anyons, group theory and planar physics
Relativistic and nonrelativistic anyons are described in a unified formalism
by means of the coadjoint orbits of the symmetry groups in the free case as
well as when there is an interaction with a constant electromagnetic field. To
deal with interactions we introduce the extended Poincar\'e and Galilei Maxwell
groups.Comment: 22 pages, journal reference added, bibliography update
Galilean Lee Model of the Delta Function Potential
The scattering cross section associated with a two dimensional delta function
has recently been the object of considerable study. It is shown here that this
problem can be put into a field theoretical framework by the construction of an
appropriate Galilean covariant theory. The Lee model with a standard Yukawa
interaction is shown to provide such a realization. The usual results for delta
function scattering are then obtained in the case that a stable particle exists
in the scattering channel provided that a certain limit is taken in the
relevant parameter space. In the more general case in which no such limit is
taken finite corrections to the cross section are obtained which (unlike the
pure delta function case) depend on the coupling constant of the model.Comment: 7 pages, latex, no figure
From Golden Spirals to Constant Slope Surfaces
In this paper, we find all constant slope surfaces in the Euclidean 3-space,
namely those surfaces for which the position vector of a point of the surface
makes constant angle with the normal at the surface in that point. These
surfaces could be thought as the bi-dimensional analogue of the generalized
helices. Some pictures are drawn by using the parametric equations we found.Comment: 11 pages, 8 figure
(In)finite extensions of algebras from their Inonu-Wigner contractions
The way to obtain massive non-relativistic states from the Poincare algebra
is twofold. First, following Inonu and Wigner the Poincare algebra has to be
contracted to the Galilean one. Second, the Galilean algebra is to be extended
to include the central mass operator. We show that the central extension might
be properly encoded in the non-relativistic contraction. In fact, any
Inonu-Wigner contraction of one algebra to another, corresponds to an infinite
tower of abelian extensions of the latter. The proposed method is
straightforward and holds for both central and non-central extensions. Apart
from the Bargmann (non-zero mass) extension of the Galilean algebra, our list
of examples includes the Weyl algebra obtained from an extension of the
contracted SO(3) algebra, the Carrollian (ultra-relativistic) contraction of
the Poincare algebra, the exotic Newton-Hooke algebra and some others. The
paper is dedicated to the memory of Laurent Houart (1967-2011).Comment: 7 pages, revtex style; v2: Minor corrections, references added; v3:
Typos correcte
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