Recovering coherence from decoherence: a method of quantum state reconstruction

We present a feasible scheme for reconstructing the quantum state of a field prepared inside a lossy cavity. Quantum coherences are normally destroyed by dissipation, but we show that at zero temperature we are able to retrieve enough information about the initial state, making possible to recover its Wigner function as well as other quasiprobabilities. We provide a numerical simulation of a Schroedinger cat state reconstruction.Comment: 8 pages, in RevTeX, 4 figures, accepted for publication in Phys. Rev. A (november 1999

Unitary transformation approach for the trapped ion dynamics

We present a way of treating the problem of the interaction of a single trapped ion with laser beams based on successive aplications of unitary transformations onto the Hamiltonian. This allows the diagonalization of the Hamiltonian, by means of recursive relations, without performing the Lamb-Dicke approximation.Comment: 8 page

Una generación energética de las condiciones de contorno en láminas de Love-Kirchhoff

Un problema clásico de la teoría de láminas de Love-Kirchhoff (lámina sin deformación transversal) reside en la correcta definición de las condiciones de contorno estáticas. Después de una serie de artículos principalmente dedicados a la presentación de teorías de láminas completas, autores exponen la obtención de las condiciones de contorno asociadas a una teoría incom.pleta como la de Love-Kirchhoff, denominada CTO en el texto, a partir de una formulación energética consistente con los trabajos anteriores.A classical problem in Love-Kirchhoff shell theory stays in statical boundary conditions definition. Following some papers mainly dedicated to the construction of complete shell theories, authors show how to obtain boundary conditions consistent with an uncomplete shell theory, as the Love-Kirchhoff theory, by an energy approach compatible with previous work.Peer Reviewe

Un elemento finito 3D para el análisis cinemáticamente no lineal de láminas elastoplásticas

En el análisis de láminas elastoplásticas se debe recurrir a temías de la plasticidad ad hoc, no derivadas de la teoría tridimensional general sino postuladas a priori y basadas en muchas simplificaciones, o bien tratar el cuerpo como 3D. En este segundo caso, la utilización de elementos convencionales en el Método de los Elementos Finitos (M.E.F.) plantea importantes problemas numéricos, y requiere un tiempo de compntación excesivamente dilatado. En este escrito se presenta un elemento finito 3D pensado especialmente para superar estos inconvenientes. Su desarrollo consta de tres partes bien diferenciadas: la obtención de las inatrices cineináticas necesarias para la resolución del problema estático de un continuo 3D cualquiera, supuesta conocida la interpolación del campo de desplazamientos; la particularización de éstas al caso laminar, mediante el uso del mode1,o de comportamiento transversal CT1 coino función de interpolación en el espesor; y la reorganización del algoritmo resultante de las dos fases anteriores para evitar el aumento desmesurado del tiempo de cálculo cuando se increiiienta el número de puntas de integración en el espesor. Finalmente se incluyen varios ejeinplos que muestran el buen comportamiento del elemento presentado, cuyas principales ventajas son: en primer lugar, que permite proceciar un elevado número de puntos de integración en el espesor con un coste computacional razonable, y a continuación, la capacidad para tratar cualquier geometría de la superficie de referencia de modo muy sencillo pero sin introducir siiiiplificaciones, y la posibilidad de tratar otros tipos estructurales derivados del laminar utilizando el misnio algoritiiio.When dealing with elastoplastic shell analysis, we must appeal either to suitable theories of plasticity, which aren't the result of the general three-dimensional theory as they have been forinulated a priori and based on many siinplifications, or to the treateinent of the body as a tliree dimensional one (3D). In tlie second case, there are a lot of numerical probleins arising from the use of conventional eleinents in the Finite Elenient Metliod (F.E.M.), and also, a long tinie of computation isrequired. In this paper we present a 3D finite element, which is aimed at overcoming the aforesaid disavantages. Its development is divided into three different parts, first of all the obtention of the kinematic matrices required to solve a static problem of whatever 3D continuous medium, once the interpolation for the displacement field is known. Secondly, their particularization to tbe shell case, through the use of the model of transversal behaviour CTl as the function of interpolation in thickness. The third one is the reorganization of the resulting algorithm from the two previous steps to avoid an excessive increase in the calculation time when the number OS integration points in thickness is raised. Finally we include severa1 examples showing the good results of the described element, having some advantages such as: first, the processing of a high number of integration points with a reasonable computational cost; secondly, the ability to deal with any reference surface geometry in a very simple way, without introducing any simplification, and in the third place, the possibility to deal with other kinds of structures derived from the shell model by using the same algorithm.Peer Reviewe

Un elemento finito 3D para el análisis cinemáticamente no lineal de láminas elastoplásticas

En el análisis de láminas elastoplásticas se debe recurrir a temías de la plasticidad ad hoc, no derivadas de la teoría tridimensional general sino postuladas a priori y basadas en muchas simplificaciones, o bien tratar el cuerpo como 3D. En este segundo caso, la utilización de elementos convencionales en el Método de los Elementos Finitos (M.E.F.) plantea importantes problemas numéricos, y requiere un tiempo de compntación excesivamente dilatado. En este escrito se presenta un elemento finito 3D pensado especialmente para superar estos inconvenientes. Su desarrollo consta de tres partes bien diferenciadas: la obtención de las inatrices cineináticas necesarias para la resolución del problema estático de un continuo 3D cualquiera, supuesta conocida la interpolación del campo de desplazamientos; la particularización de éstas al caso laminar, mediante el uso del mode1,o de comportamiento transversal CT1 coino función de interpolación en el espesor; y la reorganización del algoritmo resultante de las dos fases anteriores para evitar el aumento desmesurado del tiempo de cálculo cuando se increiiienta el número de puntas de integración en el espesor. Finalmente se incluyen varios ejeinplos que muestran el buen comportamiento del elemento presentado, cuyas principales ventajas son: en primer lugar, que permite proceciar un elevado número de puntos de integración en el espesor con un coste computacional razonable, y a continuación, la capacidad para tratar cualquier geometría de la superficie de referencia de modo muy sencillo pero sin introducir siiiiplificaciones, y la posibilidad de tratar otros tipos estructurales derivados del laminar utilizando el misnio algoritiiio.When dealing with elastoplastic shell analysis, we must appeal either to suitable theories of plasticity, which aren't the result of the general three-dimensional theory as they have been forinulated a priori and based on many siinplifications, or to the treateinent of the body as a tliree dimensional one (3D). In tlie second case, there are a lot of numerical probleins arising from the use of conventional eleinents in the Finite Elenient Metliod (F.E.M.), and also, a long tinie of computation isrequired. In this paper we present a 3D finite element, which is aimed at overcoming the aforesaid disavantages. Its development is divided into three different parts, first of all the obtention of the kinematic matrices required to solve a static problem of whatever 3D continuous medium, once the interpolation for the displacement field is known. Secondly, their particularization to tbe shell case, through the use of the model of transversal behaviour CTl as the function of interpolation in thickness. The third one is the reorganization of the resulting algorithm from the two previous steps to avoid an excessive increase in the calculation time when the number OS integration points in thickness is raised. Finally we include severa1 examples showing the good results of the described element, having some advantages such as: first, the processing of a high number of integration points with a reasonable computational cost; secondly, the ability to deal with any reference surface geometry in a very simple way, without introducing any simplification, and in the third place, the possibility to deal with other kinds of structures derived from the shell model by using the same algorithm.Peer Reviewe

Sensitivity of the g-mode frequencies to pulsation codes and their parameters

From the recent work of the Evolution and Seismic Tools Activity (ESTA, Lebreton et al. 2006; Monteiro et al. 2008), whose Task 2 is devoted to compare pulsational frequencies computed using most of the pulsational codes available in the asteroseismic community, the dependence of the theoretical frequencies with non-physical choices is now quite well fixed. To ensure that the accuracy of the computed frequencies is of the same order of magnitude or better than the observational errors, some requirements in the equilibrium models and the numerical resolutions of the pulsational equations must be followed. In particular, we have verified the numerical accuracy obtained with the Saclay seismic model, which is used to study the solar g-mode region (60 to 140$\mu$Hz). We have compared the results coming from the Aarhus adiabatic pulsation code (ADIPLS), with the frequencies computed with the Granada Code (GraCo) taking into account several possible choices. We have concluded that the present equilibrium models and the use of the Richardson extrapolation ensure an accuracy of the order of $0.01 \mu Hz$ in the determination of the frequencies, which is quite enough for our purposes.Comment: 10 pages, 5 figures, accepted in Solar Physic

Clustered spatially and temporally resolved global heat and cooling energy demand in the residential sector

Climatic conditions, population density, geography, and settlement structure all have a strong influence on the heating and cooling demand of a country, and thus on resulting energy use and greenhouse gas emissions. In particular, the choice of heating or cooling system is influenced by available energy distribution infrastructure, where the cost of such infrastructure is strongly related to the spatial density of the demand. As such, a better estimation of the spatial and temporal distribution of demand is desirable to enhance the accuracy of technology assessment. This paper presents a Geographical Information System methodology combining the hourly NASA MERRA-2 global temperature dataset with spatially resolved population data and national energy balances to determine global high-resolution heat and cooling energy density maps. A set of energy density bands is then produced for each country using K-means clustering. Finally, demand profiles representing diurnal and seasonal variations in each band are derived to capture the temporal variability. The resulting dataset for 165 countries, published alongside this article, is designed to be integrated into a new integrated assessment model called MUSE (ModUlar energy systems Simulation Environment)but can be used in any national heat or cooling technology analysis. These demand profiles are key inputs for energy planning as they describe demand density and its fluctuations via a consistent method for every country where data is available

Evaluation of point defect concentrations in B2-FeAl intermetallic compound

Thermal defects are studied for three compositions (49, 50 and 52 at.%Fe) of the intermetallic compound FeAl with B2 structure. Magnetic measurements are used to determine the thermal defect concentrations. These concentrations are determined from fitting the experimental curves of magnetic susceptibility, obtained during an isochronal annealing after a quench. Next we have evaluated theoretically the concentrations of different point defects that exist in this compound. The used model is based in the Bragg-Williams approximation assuming the nearest-neighbour interaction. The calculated concentrations describe well the experimental values.Thermal defects are studied for three compositions (49, 50 and 52 at.%Fe) of the intermetallic compound FeAl with B2 structure. Magnetic measurements are used to determine the thermal defect concentrations. These concentrations are determined from fitting the experimental curves of magnetic susceptibility, obtained during an isochronal annealing after a quench. Next we have evaluated theoretically the concentrations of different point defects that exist in this compound. The used model is based in the Bragg-Williams approximation assuming the nearest-neighbour interaction. The calculated concentrations describe well the experimental values