7,722 research outputs found
Multi-species grandcanonical models for networks with reciprocity
Reciprocity is a second-order correlation that has been recently detected in
all real directed networks and shown to have a crucial effect on the dynamical
processes taking place on them. However, no current theoretical model generates
networks with this nontrivial property. Here we propose a grandcanonical class
of models reproducing the observed patterns of reciprocity by regarding single
and double links as Fermi particles of different `chemical species' governed by
the corresponding chemical potentials. Within this framework we find
interesting special cases such as the extensions of random graphs, the
configuration model and hidden-variable models. Our theoretical predictions are
also in excellent agreement with the empirical results for networks with well
studied reciprocity.Comment: 4 pages, 1 figur
Ladder exponentiation for generic large symmetric representation Wilson loops
A recent proposal was made for a large representation rank limit for which
the expectation values of N = 4 super Yang-Mills Wilson loops are given by the
exponential of the 1-loop result. We verify the validity of this exponentiation
in the strong coupling limit using the holographic D3-brane description for
straight Wilson loops following an arbitrary internal space trajectory.Comment: 12 pages, 1 figur
Generalized Bose-Fermi statistics and structural correlations in weighted networks
We derive a class of generalized statistics, unifying the Bose and Fermi
ones, that describe any system where the first-occupation energies or
probabilities are different from subsequent ones, as in presence of thresholds,
saturation, or aging. The statistics completely describe the structural
correlations of weighted networks, which turn out to be stronger than expected
and to determine significant topological biases. Our results show that the null
behavior of weighted networks is different from what previously believed, and
that a systematic redefinition of weighted properties is necessary.Comment: Final version accepted for publication on Physical Review Letter
Quantum non-Markovian behavior at the chaos border
In this work we study the non-Markovian behaviour of a qubit coupled to an
environment in which the corresponding classical dynamics change from
integrable to chaotic. We show that in the transition region, where the
dynamics has both regular islands and chaotic areas, the average non-Markovian
behaviour is enhanced to values even larger than in the regular regime. This
effect can be related to the non-Markovian behaviour as a function of the the
initial state of the environment, where maxima are attained at the regions
dividing separate areas in classical phase space, particularly at the borders
between chaotic and regular regions. Moreover, we show that the fluctuations of
the fidelity of the environment -- which determine the non-Markovianity measure
-- give a precise image of the classical phase portrait.Comment: 23 pages, 9 figures (JPA style). Closest to published versio
Quantum Singular Value Decomposer
We present a variational quantum circuit that produces the Singular Value
Decomposition of a bipartite pure state. The proposed circuit, that we name
Quantum Singular Value Decomposer or QSVD, is made of two unitaries
respectively acting on each part of the system. The key idea of the algorithm
is to train this circuit so that the final state displays exact output
coincidence from both subsystems for every measurement in the computational
basis. Such circuit preserves entanglement between the parties and acts as a
diagonalizer that delivers the eigenvalues of the Schmidt decomposition. Our
algorithm only requires measurements in one single setting, in striking
contrast to the settings required by state tomography. Furthermore, the
adjoints of the unitaries making the circuit are used to create the
eigenvectors of the decomposition up to a global phase. Some further
applications of QSVD are readily obtained. The proposed QSVD circuit allows to
construct a SWAP between the two parties of the system without the need of any
quantum gate communicating them. We also show that a circuit made with QSVD and
CNOTs acts as an encoder of information of the original state onto one of its
parties. This idea can be reversed and used to create random states with a
precise entanglement structure.Comment: 6 + 1 pages, 5 figure
Case study the poultry industry in Colombia
"As developing countries open their economies further to trade, their food industries are striving to raise safety and quality standards in order to compete in new markets. Such is the case with the Colombian poultry industry... Critical questions face the Colombian poultry industry: Is it ready to compete with foreign poultry producers on price, quality, and safety? Can industry efforts to produce better quality products assure an increased share of domestic and regional markets? This brief reviews the private initiatives undertaken by the Colombian poultry industry to assure food safety in light of these questions." from TextFood safety ,food security ,Public health ,
How can the effects of the introduction of a new airline on a national airline network be measured? A time series approach for the Ryanair case in Spain
This paper quantifies the Ryanair Effect on the Spanish airline network. It proposes new methodology
based on an advanced time series approach that allows both the direct and indirect effects of the
incorporation of a new airline to be measured and that can be easily extrapolated to other airport
systems. The findings show the mean indirect effect on other airlines, in absolute value, is 8.6 per
cent of the total airport traffic, peaking at a maximum of almost 29 per cent. Also, surprisingly,
there is found to be a negative indirect effect at only four of the ten airports analysed
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