131 research outputs found
Clustering stock market companies via chaotic map synchronization
A pairwise clustering approach is applied to the analysis of the Dow Jones
index companies, in order to identify similar temporal behavior of the traded
stock prices. To this end, the chaotic map clustering algorithm is used, where
a map is associated to each company and the correlation coefficients of the
financial time series are associated to the coupling strengths between maps.
The simulation of a chaotic map dynamics gives rise to a natural partition of
the data, as companies belonging to the same industrial branch are often
grouped together. The identification of clusters of companies of a given stock
market index can be exploited in the portfolio optimization strategies.Comment: 12 pages, 3 figure
Reduced coherence in double-slit diffraction of neutrons
In diffraction experiments with particle beams, several effects lead to a
fringe visibility reduction of the interference pattern. We theoretically
describe the intensity one can measure in a double-slit setup and compare the
results with the experimental data obtained with cold neutrons. Our conclusion
is that for cold neutrons the fringe visibility reduction is due not to
decoherence, but to initial incoherence.Comment: 4 pages LaTeX, 2 figure
Hausdorff clustering of financial time series
A clustering procedure, based on the Hausdorff distance, is introduced and
tested on the financial time series of the Dow Jones Industrial Average (DJIA)
index.Comment: 9 pages, 3 figure
Universal Leakage Elimination
``Leakage'' errors are particularly serious errors which couple states within
a code subspace to states outside of that subspace thus destroying the error
protection benefit afforded by an encoded state. We generalize an earlier
method for producing leakage elimination decoupling operations and examine the
effects of the leakage eliminating operations on decoherence-free or noiseless
subsystems which encode one logical, or protected qubit into three or four
qubits. We find that by eliminating the large class of leakage errors, under
some circumstances, we can create the conditions for a decoherence free
evolution. In other cases we identify a combination decoherence-free and
quantum error correcting code which could eliminate errors in solid-state
qubits with anisotropic exchange interaction Hamiltonians and enable universal
quantum computing with only these interactions.Comment: 14 pages, no figures, new version has references updated/fixe
Timelapse
We discuss the existence in an arbitrary frame of a finite time for the
transformation of an initial quantum state into another e.g. in a decay.
This leads to the introduction of a timelapse in analogy with
the lifetime of a particle. An argument based upon the Heisenberg uncertainty
principle suggests the value of . Consequences for the
exponential decay formula and the modifications that introduces
into the Breit-Wigner mass formula are described.Comment: 5 pages [2 figs], ReV-Te
Quantum Zeno subspaces
The quantum Zeno effect is recast in terms of an adiabatic theorem when the
measurement is described as the dynamical coupling to another quantum system
that plays the role of apparatus. A few significant examples are proposed and
their practical relevance discussed. We also focus on decoherence-free
subspaces.Comment: 5 pages, 1 figure, to be published in Phys. Rev. Let
Phenomenology of Sterile Neutrinos
The indications in favor of short-baseline neutrino oscillations, which
require the existence of one or more sterile neutrinos, are reviewed. In the
framework of 3+1 neutrino mixing, which is the simplest extension of the
standard three-neutrino mixing which can partially explain the data, there is a
strong tension in the interpretation of the data, mainly due to an
incompatibility of the results of appearance and disappearance experiments. In
the framework of 3+2 neutrino mixing, CP violation in short-baseline
experiments can explain the difference between MiniBooNE neutrino and
antineutrino data, but the tension between the data of appearance and
disappearance experiments persists because the short-baseline disappearance of
electron antineutrinos and muon neutrinos compatible with the LSND and
MiniBooNE antineutrino appearance signal has not been observed.Comment: 8 pages. Invited paper to NUFACT 11, XIIIth International Workshop on
Neutrino Factories, Super beams and Beta beams, 1-6 August 2011, CERN and
University of Geneva (Submitted to IOP conference series
Zeno dynamics yields ordinary constraints
The dynamics of a quantum system undergoing frequent measurements (quantum
Zeno effect) is investigated. Using asymptotic analysis, the system is found to
evolve unitarily in a proper subspace of the total Hilbert space. For spatial
projections, the generator of the "Zeno dynamics" is the Hamiltonian with
Dirichlet boundary conditions.Comment: 6 page
Hausdorff clustering
A clustering algorithm based on the Hausdorff distance is introduced and
compared to the single and complete linkage. The three clustering procedures
are applied to a toy example and to the time series of financial data. The
dendrograms are scrutinized and their features confronted. The Hausdorff
linkage relies of firm mathematical grounds and turns out to be very effective
when one has to discriminate among complex structures.Comment: 12 pages, 13 figure
Values in the EU Charter of Fundamental Rights : A Legal-Philosophical Analysis with a Focus on Migrants’ Rights
This work provides a sketch of a legal-philosophical understanding of the normative content of the Charter of Fundamental Rights of the European Union. In particular, after brefly reconstructing the genesis of the Charter and its historical and philosophical background, it focuses on how the values of dignity, freedom, equality and solidarity are conceived in the Charter and implemented in both Union law and the case law of the Court of Justice. Special attention is also devoted to the relationship between the European Union\u2019s and the Council of Europe\u2019s systems of protection of fundamental rights, with particular reference to the jurisprudence of the European Court of Human Rights. This work stems from the research project "NoVaMigra \u2013 Norms and Values in the European Migration and Refugee Crisis", funded by the European Unionis. Accordingly, it mainly focuses on those rights which are, or could be, particularly significant in relation to migrants, asylum seekers and refugees. Furthermore, special attention is devoted to women\u2019s rights and gender equality
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