6,260 research outputs found
Ensembles based on the Rich-Club and how to use them to build soft-communities
16 pages, 5 figures16 pages, 5 figures16 pages, 5 figuresEnsembles of networks are used as null-models to discriminate network structures. We present an efficient algorithm, based on the maximal entropy method to generate network ensembles defined by the degree sequence and the rich-club coefficient. The method is applicable for unweighted, undirected networks. The ensembles are used to generate correlated and uncorrelated null--models of a real networks. These ensembles can be used to define the partition of a network into soft communities
Neutrino masses and mixings in a Minimal S_3-invariant Extension of the Standard Model
The mass matrices of the charged leptons and neutrinos, that had been derived
in the framework of a Minimal S_3-invariant Extension of the Standard Model,
are here reparametrized in terms of their eigenvalues. The neutrino mixing
matrix, V_PMNS, is then computed and exact, explicit analytical expressions for
the neutrino mixing angles as functions of the masses of the neutrinos and
charged leptons are obtained. The reactor, theta_13, and the atmosferic,
theta_23, mixing angles are found to be functions only of the masses of the
charged leptons. The numerical values of theta_13{th} and theta_23{th} computed
from our theoretical expressions are found to be in excellent agreement with
the latest experimental determinations. The solar mixing angle, theta_12{th},
is found to be a function of both, the charged lepton and neutrino masses, as
well as of a Majorana phase phi_nu. A comparison of our theoretical expression
for the solar angle theta_12{th} with the latest experimental value
theta_12{exp} ~ 34 deg allowed us to fix the scale and origin of the neutrino
mass spectrum and obtain the mass values |m_nu1|=0.0507 eV, |m_nu2|=0.0499 eV
and |m_nu3|=0.0193 eV, in very good agreement with the observations of neutrino
oscillations, the bounds extracted from neutrinoless double beta decay and the
precision cosmological measurements of the CMB.Comment: To appear in the Proceedings of the XXIX Symposium on Nuclear
Physics, Cocoyoc, Mex., January 2006. Some typographical errors on formulae
correcte
Models of flavour with discrete symmetries
We briefly review some recent developments in theoretical models of fermion
masses, mixings and CP violation with discrete non-Abelian symmetries. Then, we
explain the main ideas of a recently proposed Minimal S_3 Invariant Extension
of the Standard Model and its application to a unified analysis of masses,
mixings and CP violation in the leptonic and quark sectors as well as the
explicit computation of the V_PMNS and V_CKM mixing matrices.Comment: Latex, 17 pages, no figure
The Rich-Club Phenomenon In The Internet Topology
We show that the Internet topology at the Autonomous System (AS) level has a
rich--club phenomenon. The rich nodes, which are a small number of nodes with
large numbers of links, are very well connected to each other. The rich--club
is a core tier that we measured using the rich--club connectivity and the
node--node link distribution. We obtained this core tier without any heuristic
assumption between the ASes. The rich--club phenomenon is a simple qualitative
way to differentiate between power law topologies and provides a criterion for
new network models. To show this, we compared the measured rich--club of the AS
graph with networks obtained using the Barab\'asi--Albert (BA) scale--free
network model, the Fitness BA model and the Inet--3.0 model.Comment: To be appeared in the IEEE Communications Letter
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