4,886 research outputs found
Tensorial characterization and quantum estimation of weakly entangled qubits
In the case of two qubits, standard entanglement monotones like the linear
entropy fail to provide an efficient quantum estimation in the regime of weak
entanglement. In this paper, a more efficient entanglement estimation, by means
of a novel class of entanglement monotones, is proposed. Following an approach
based on the geometric formulation of quantum mechanics, these entanglement
monotones are defined by inner products on invariant tensor fields on bipartite
qubit orbits of the group SU(2)xSU(2).Comment: 23 pages, 3 figure
Stellar laboratories. V. The Xe VI ultraviolet spectrum and the xenon abundance in the hot DO-type white dwarf RE0503-289
For the spectral analysis of spectra of hot stars with a high resolution and
high signal-to-noise ratio (S/N), advanced non-local thermodynamic equilibrium
(NLTE) model atmospheres are mandatory. These are strongly dependent on the
reliability of the atomic data that are used for their calculation.
Reliable Xe VI oscillator strengths are used to identify Xe lines in the
ultraviolet spectrum of the DO-type white dwarf RE0503-289 and to determine its
photospheric Xe abundance.
We publish newly calculated oscillator strengths that are based on a recently
measured Xe VI laboratory line spectrum. These strengths were used to consider
their radiative and collisional bound-bound transitions in detail in our NLTE
stellar-atmosphere models to analyze Xe VI lines exhibited in high-resolution
and high S/N UV observations of RE0503-289.
We identify three hitherto unknown Xe VI lines in the ultraviolet spectrum of
RE0503-289 and confirm the previously measured photospheric Xe abundance of
this white dwarf (log Xe = -4.2 +/- 0.6).
Reliable measurements and calculations of atomic data are prerequisite for
stellar-atmosphere modeling. Observed Xe VI line profiles in the ultraviolet
spectrum of the white dwarf RE0503-289 were well reproduced with the newly
calculated Xe VI oscillator strengths.Comment: 3 pages, 4 figure
Comment on "Correlated electron-nuclear dynamics: Exact factorization of the molecular wavefunction" [J. Chem. Phys. 137, 22A530 (2012)]
In spite of the relevance of the proposal introduced in the recent work A.
Abedi, N. T. Maitra and E. K. U. Gross, J. Chem. Phys. 137, 22A530, 2012, there
is an important ingredient which is missing. Namely, the proof that the norms
of the electronic and nuclear wavefunctions which are the solutions to the
nonlinear equations of motion are preserved by the evolution. To prove the
conservation of these norms is precisely the objective of this Comment.Comment: 2 pages, published versio
Simultaneous analysis of elastic scattering and transfer/breakup channels for the 6He+208Pb reaction at energies near the Coulomb barrier
The elastic and alpha-production channels for the 6He+208Pb reaction are
investigated at energies around the Coulomb barrier (E_{lab}=14, 16, 18, 22,
and 27 MeV). The effect of the two-neutron transfer channels on the elastic
scattering has been studied within the Coupled-Reaction-Channels (CRC) method.
We find that the explicit inclusion of these channels allows a simultaneous
description of the elastic data and the inclusive alpha cross sections at
backward angles. Three-body Continuum-Discretized Coupled-Channels (CDCC)
calculations are found to reproduce the elastic data, but not the
transfer/breakup data. The trivially-equivalent local polarization potential
(TELP) derived from the CRC and CDCC calculations are found to explain the
features found in previous phenomenological optical model calculations for this
system.Comment: 7 pages, 6 figures (replaced with updated version
Classical Tensors and Quantum Entanglement I: Pure States
The geometrical description of a Hilbert space asociated with a quantum
system considers a Hermitian tensor to describe the scalar inner product of
vectors which are now described by vector fields. The real part of this tensor
represents a flat Riemannian metric tensor while the imaginary part represents
a symplectic two-form. The immersion of classical manifolds in the complex
projective space associated with the Hilbert space allows to pull-back tensor
fields related to previous ones, via the immersion map. This makes available,
on these selected manifolds of states, methods of usual Riemannian and
symplectic geometry. Here we consider these pulled-back tensor fields when the
immersed submanifold contains separable states or entangled states. Geometrical
tensors are shown to encode some properties of these states. These results are
not unrelated with criteria already available in the literature. We explicitly
deal with some of these relations.Comment: 16 pages, 1 figure, to appear in Int. J. Geom. Meth. Mod. Phy
Coubertin and the artistic competitions in the Modern Olympic Games
El objetivo de este trabajo es analizar la importancia que tenía para
Coubertin la inclusión de concursos artísticos en el programa oficial de los
Juegos Olímpicos modernos. Se estudiará cómo, cuándo y por qué surgió la idea
en Coubertin de unir de manera armoniosa las artes y las letras a los Juegos
Olímpicos, como ya ocurriera en la antigua Olimpia. En los Juegos Olímpicos de
Estocolmo de 1912, se celebraron por primera vez competiciones deportivas y
concursos artísticos, cumpliéndose el anhelo de Coubertin. Sin embargo,
después de siete citas olímpicas en las que se habían celebrado concursos
artísticos, el COI decidió suprimirlos en 1949, sustituyéndolos por “Olimpíadas
Culturales”, “exhibiciones” o “exposiciones”. La metodología de este estudio es
histórica y se fundamenta en fuentes primarias y secundarias. Como conclusión,
para Coubertin fueron tan importantes los concursos artísticos en los Juegos
Olímpicos modernos que tuvieron el mismo rango que las competiciones
deportivasThe aim of this essay is to analyse the importance that Coubertin gave to
including the artistic competitions in the official programme of the modern
Olympic Games. It will be studied how, when and why Coubertin's idea of
harmoniously joining arts and letters to the Olympic Games appeared, as it had
already happened in ancient Olympia. In the Olympic Games of Stockholm
1912, sport and artistic competitions were celebrated for the first time, fulfilling
thus Coubertin's longing. However, after seven Olympic events where artistic
competitions had been held, the IOC decided to eliminate them in 1949 and to
replace them for "Cultural Olympics", "exhibitions" or "expositions". The
methodology of this study is historical and based on primary and secondary
sources. In conclusion, to Coubertin the artistic competitions in the modern
Olympic Games were so important as to have the same status as the sport
competition
La práctica del ciclismo indoor en los mayores: implicaciones metodológicas
Uno de los cambios más característicos de la época tecnológica en la que nos encontramos inmersos, es el envejecimiento de la población y la consecuente inversión de la pirámide poblacional. Dicha inversión, acentúa la necesidad de diseñar y extender planes de actuación que promuevan actividades físico-recreativas continuadas con intensidades, cargas y ejercicios específicos totalmente adaptados a las características de esta población. La propuesta que aquí presentamos se basa en la práctica del ciclo indoor, que representa una experiencia fundamental para el desarrollo integral de la persona. Esta práctica puede considerarse una terapia imprescindible para la estimulación y reeducación de las habilidades concretas de esta población, así como para la adquisición de técnicas de comunicación social, a la vez que realizan una actividad lúdica y placentera. Mediante un programa de actividad física de este tipo, se pretende aumentar las posibilidades funcionales, al tiempo que se mejora las psico-afectivas, y con ello la calidad de vida de nuestros mayores
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