Spin state in the propagation of quantum relativistic particles along classical trajectories

We address the propagation of the spin along classical trajectories for a 1/2-spin particle obeying the Dirac equation with scalar potentials. Focusing on classical trajectories as the exact propagation of wave-function discontinuities we find an explicit spin-transport law for the case of the Dirac oscillator. In the general case we examine the spin propagation along classical trajectories emerging as an approximation of the quantum dynamics via the mechanical analog of the optical eikonal asymptotic approach. Throughout we establish as many parallels as possible with the equivalent situation for the electromagnetic field.Comment: 8 pages, 5 figure

Multi-feature Bottom-up Processing and Top-down Selection for an Object-based Visual Attention Model

Artificial vision systems can not process all the information that they receive from the world in real time because it is highly expensive and inefficient in terms of computational cost. However, inspired by biological perception systems, it is possible to develop an artificial attention model able to select only the relevant part of the scene, as human vision does. This paper presents an attention model which draws attention over perceptual units of visual information, called proto-objects, and which uses a linear combination of multiple low-level features (such as colour, symmetry or shape) in order to calculate the saliency of each of them. But not only bottom-up processing is addressed, the proposed model also deals with the top-down component of attention. It is shown how a high-level task can modulate the global saliency computation, modifying the weights involved in the basic features linear combination.Ministerio de Economía y Competitividad (MINECO), proyectos: TIN2008-06196 y TIN2012-38079-C03-03. Campus de Excelencia Internacional Andalucía Tech

Quantum Scale Estimation

Quantum scale estimation, as introduced and explored here, establishes the most precise framework for the estimation of scale parameters which is allowed by the laws of quantum mechanics. This addresses an important gap in quantum metrology, since current practice focuses almost exclusively on the estimation of phase and location parameters. For given prior probability and quantum state, and using Bayesian principles, a rule to construct the optimal probability-operator measurement is provided. Furthermore, the corresponding minimum mean logarithmic error is identified. This is then generalised as to accommodate the simultaneous estimation of multiple scale parameters, and a procedure to classify practical measurements into optimal, almost-optimal or sub-optimal is highlighted. As an application, the framework of scale-invariant global thermometry is revisited and generalised. On a more conceptual note, the optimal strategy is employed to construct an observable for scale parameters, an approach which may serve as a template for a more systematic search of quantum observables. Quantum scale estimation thus opens a new line of enquire - the precise measurement of scale parameters such as temperatures and rates - within the quantum information sciences.Comment: 15 pages, 1 table. More explicit definition of scale parameter. Manuscript updated accordingly, but same results. Multi-shot subsection removed for simplicity. Discussion of quantum thermometry protocols considerably expande

How Structural Are Structural Parameters?

This paper studies how stable over time are the so-called "structural parameters" of dynamic stochastic general equilibrium (DSGE) models. To answer this question, we estimate a medium-scale DSGE model with real and nominal rigidities using U.S. data. In our model, we allow for parameter drifting and rational expectations of the agents with respect to this drift. We document that there is strong evidence that parameters change within our sample. We illustrate variations in the parameters describing the monetary policy reaction function and in the parameters characterizing the pricing behavior of firms and households. Moreover, we show how the movements in the pricing parameters are correlated with inflation. Thus, our results cast doubts on the empirical relevance of Calvo models.

Tendencias en la atención a la discapacidad

La atención a las personas con discapacidad ha evolucionado, especialmente desde el siglo XX. El principal agente prestador de servicios a las personas con discapacidad es la familia. La atención desde las Instituciones está repartida según las competencias de cada administración. El movimiento de vida independiente plantea el respeto de los derechos de ciudadanía de las personas con discapacidad.Ezinduei arreta emateak bilakaera izan du XX. mendetik aurrera bereziki. Ezinduei zerbitzuak eskaintzeko eragile nagusia familia izan da. Instituzioen arreta administrazio bakoitzaren eskumenen arabera banatuta dago. Bizimodu independienterako mugimenduak ezinduen herritartasun eskubidea errespetatzea planteatzen du.L'attention aux personnes handicapées a évolué, spécialement depuis le XXème siècle. C'est la famille qui prête principalement ses services aux personnes handicapées. L'attention depuis les Institutions est répartie selon les compétences de chaque administration. Le mouvement de vie indépendante établit le respect des droits de citoyenneté des personnes handicapées.Care for impaired people has evolved, especially since the 20th century. The main agents to provide services to impaired people are their own families. The services provided by Public Administrations are distributed according to their competencies. The movement towards an independent life proposes to respect impaired people's rights as citizens

Estimating dynamic equilibrium economies: linear versus nonlinear likelihood

This paper compares two methods for undertaking likelihood-based inference in dynamic equilibrium economies: a sequential Monte Carlo filter proposed by Fernández-Villaverde and Rubio-Ramírez (2004) and the Kalman filter. The sequential Monte Carlo filter exploits the nonlinear structure of the economy and evaluates the likelihood function of the model by simulation methods. The Kalman filter estimates a linearization of the economy around the steady state. The authors report two main results. First, both for simulated and for real data, the sequential Monte Carlo filter delivers a substantially better fit of the model to the data as measured by the marginal likelihood. This is true even for a nearly linear case. Second, the differences in terms of point estimates, even if relatively small in absolute values, have important effects on the moments of the model. The authors conclude that the nonlinear filter is a superior procedure for taking models to the data.

On the solution of the growth model with investment-specific technological change

Recent work by Greenwood, Hercowitz, and Krusell (1997 and 2000) and Fisher (2003) has emphasized the importance of investment-specific technological change as a main driving force behind long-run growth and the business cycle. This paper shows how the growth model with investment-specific technological change has a closed-form solution if capital fully depreciates. This solution furthers our understanding of the model, and it constitutes a useful benchmark to check the accuracy of numerical procedures to solve dynamic macroeconomic models in cases with several state variables.

La Ilustración de Madrid (1870-1871). Revista de transición del romanticismo al realismo

La Ilustración de Madrid (1870-1871) fue una revista que trató de aunar información política y cultural con una presentación gráfica cuidada, realizada por artistas españoles. Dirigida por Gustavo Adolfo Bécquer e impulsada en su parte gráfica por Valeriano Bécquer, la revista perdió en gran parte su orientación cuando fallecieron los dos hermanos, Valeriano en septiembre y Gustavo Adolfo en diciembre de 1870. Aun así sobrevivió una año más y resulta hoy una de las publicaciones periódicas fundamentales para el estudio de la transición del romanticismo al realismo.La Ilustración de Madrid (1870-1871) (Enlightenment in Madrid) was a magazine that tried to unite political and cultural information with a delicate graphics presentation from Spanish artists. It was directed by Gustavo Adolfo Bécquer and promoted by Valeriano Bécquer in its graphic side. The magazine lost a big part of situation when the two brothers, Valeriano in September and Gustavo Adolfo in December of 1870, passed away. Even so it survived a year longer and it is considered one of the most fundamental journalistic publications of the study of the transition from romanticism to realism