5,107 research outputs found
The 125 GeV boson: A composite scalar?
Assuming that the 125 GeV particle observed at the LHC is a composite scalar
and responsible for the electroweak gauge symmetry breaking, we consider the
possibility that the bound state is generated by a non-Abelian gauge theory
with dynamically generated gauge boson masses and a specific chiral symmetry
breaking dynamics motivated by confinement. The scalar mass is computed with
the use of the Bethe-Salpeter equation and its normalization condition as a
function of the SU(N) group and the respective fermionic representation. If the
fermions that form the composite state are in the fundamental representation of
the SU(N) group, we can generate such light boson only for one specific number
of fermions for each group. In the case of small groups, like SU(2) to SU(5),
and two fermions in the adjoint representation we find that is quite improbable
to generate such light composite scalar.Comment: 24 pages, 5 figures, discussion extended, references added; version
to appear in Phys. Rev.
An approximation scheme for an Eikonal Equation with discontinuous coefficient
We consider the stationary Hamilton-Jacobi equation where the dynamics can
vanish at some points, the cost function is strictly positive and is allowed to
be discontinuous. More precisely, we consider special class of discontinuities
for which the notion of viscosity solution is well-suited. We propose a
semi-Lagrangian scheme for the numerical approximation of the viscosity
solution in the sense of Ishii and we study its properties. We also prove an
a-priori error estimate for the scheme in an integral norm. The last section
contains some applications to control and image processing problems
Correlating the interstellar magnetic field with protostellar jets and its sources
This article combines new CCD polarimetric data with previous information
about protostellar objects in a search for correlations involving the
interstellar magnetic field. Specifically, we carried out an optical
polarimetric study of a sample of 28 fields of 10 X 10 arcmin^2 located in the
neighborhood of protostellar jets and randomly spread over the Galaxy. The
polarimetry of a large number of field stars is used to estimate both the
average and dispersion of the interstellar magnetic field (ISMF) direction in
each region. The results of the applied statistical tests are as follows.
Concerning the alignment between the jet direction and the interstellar
magnetic field, the whole sample does not show alignment. There is, however, a
statistically significant alignment for objects of Classes 0 and I. Regarding
the interstellar magnetic field dispersion, our sample presents values slightly
larger for regions containing T Tauri objects than for those harboring younger
protostars. Moreover the ISMF dispersion in regions containing high-mass
objects tends to be larger than in those including only low-mass protostars. In
our sample, the mean interstellar polarization as a function of the average
interstellar extinction in a region reaches a maximum value around 3% for A(V)
= 5, after which it decreases. Our data also show a clear correlation of the
mean value of the interstellar polarization with the dispersion of the
interstellar magnetic field: the larger the dispersion, the smaller the
polarization. Based on a comparison of our and previous results, we suggest
that the dispersion in regions forming stars is larger than in quiescent
regions.Comment: ApJ accepte
On the determination of constitutive parametersin a hyperelastic model for a soft tissue
The aim of this paper is to study a model of hyperelastic materials and itsapplications into soft tissue mechanics. In particular, we first determine an unbounded domain of the constitutive parameters of the model making our smoothstrain energy function to be polyconvex and hence satisfying the Legendre–Hadamard condition. Thus, physically reasonable material behaviour are described by our model with these parameters and a plently of tissues can betreated. Furthermore, we localize bounded subsets of constitutive parameters in fixed physical and very general bounds and then introduce a family of descrete stress–strain curves. Whence, various classes of tissues are characterized. Ourgeneral approach is based on a detailed analytical study of the first Piola–Kirchhoff stress tensor through its dependence on the invariants and on the constitutive parameters. The uniqueness of parameters for one tissue is discussed by introducing the notion of manifold of constitutive parameters, whichis locally represented by possibly different physical quantities. The advantage of our study is that we show a possible way to improve of the usual approachesshown in the literature which are mainly based on the minimization of a costfunction as the difference between experimental and model results
Lobby index as a network centrality measure
We study the lobby index (l-index for short) as a local node centrality
measure for complex networks. The l-inde is compared with degree (a local
measure), betweenness and Eigenvector centralities (two global measures) in the
case of biological network (Yeast interaction protein-protein network) and a
linguistic network (Moby Thesaurus II). In both networks, the l-index has poor
correlation with betweenness but correlates with degree and Eigenvector. Being
a local measure, one can take advantage by using the l-index because it carries
more information about its neighbors when compared with degree centrality,
indeed it requires less time to compute when compared with Eigenvector
centrality. Results suggests that l-index produces better results than degree
and Eigenvector measures for ranking purposes, becoming suitable as a tool to
perform this task.Comment: 11 pages, 4 figures. arXiv admin note: substantial text overlap with
arXiv:1005.480
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