From Complex to Stochastic Potential: Heavy Quarkonia in the Quark-Gluon Plasma

The in-medium physics of heavy quarkonium is an ideal proving ground for our ability to connect knowledge about the fundamental laws of physics to phenomenological predictions. One possible route to take is to attempt a description of heavy quark bound states at finite temperature through a Schrödinger equation with an instantaneous potential. Here we review recent progress in devising a comprehensive approach to define such a potential from first principles QCD and extract its, in general complex, values from non-perturbative lattice QCD simulations. Based on the theory of open quantum systems we will show how to interpret the role of the imaginary part in terms of spatial decoherence by introducing the concept of a stochastic potential. Shortcomings as well as possible paths for improvement are discussed.

ARMin - robot for rehabilitation of the upper extremities

Task-oriented repetitive movements can improve motor recovery in patients with neurological or orthopaedic lesions. The application of robotics can serve to assist, enhance, evaluate, and document neurological and orthopaedic rehabilitation. ARMin is a new robot for arm therapy applicable to the training of activities of daily living in clinics. ARMin has a semiexoskeletal structure with six degrees of freedom, and is equipped with position and force sensors. The mechanical structure, the actuators and the sensors of the robot are optimized for patient-cooperative control strategies based on impedance and admittance architectures. This paper describes the mechanical structure, the control system, the sensors and actuators, safety aspects and results of a first pilot study with hemiplegic and spinal cord injured subjects.

Temporal mesonic correlators at NLO for any quark mass

We present NLO results for thermal imaginary-time correlators in the vector and scalar channels as a function of the quark mass. The range of quark masses for which a non-relativistic approximation works in the temperature range considered is estimated, and charm quarks turn out to be a borderline case. Comparing with simulation data from fine lattices, we find good agreement in the vector channel but a substantial discrepancy in the scalar one. An explanation for the discrepancy is suggested in terms of physics of the quark-antiquark threshold region. Perturbative predictions for the bottom scalar spectral function around the threshold are also briefly reviewed.

Benchmarking the Bayesian reconstruction of the non-perturbative heavy ǪǬ potential

The extraction of the finite temperature heavy quark potential from lattice QCD relies on a spectral analysis of the real-time Wilson loop. Through its position and shape, the lowest lying spectral peak encodes the real and imaginary part of this complex potential. We benchmark this extraction strategy using leading order hard-thermal loop (HTL) calculations. I.e. we analytically calculate the Wilson loop and determine the corresponding spectrum. By fitting its lowest lying peak we obtain the real- and imaginary part and confirm that the knowledge of the lowest peak alone is sufficient for obtaining the potential. We deploy a novel Bayesian approach to the reconstruction of spectral functions to HTL correlators in Euclidean time and observe how well the known spectral function and values for the real and imaginary part are reproduced. Finally we apply the method to quenched lattice QCD data and perform an improved estimate of both real and imaginary part of the non-perturbative heavy ǪǬ potential.

Cartografías de la ciudad. Representación y estilización lingüística en mapas mentales de Buenos Aires

Desde un enfoque constructivista del espacio urbano como producto social, en el presente artículo presentamos algunos aspectos teóricos y metodológicos para el análisis de las representaciones geosociales y la identidad urbana para luego investigar a partir de una selección de mapas mentales la imagen espacial que los hablantes expresan a través de las variedades lingüísticas que distinguen, estilizan y ubican en su cartografía mental de la ciudad. Se trata de un primer acercamiento a un corpus recopilado en 2013, que permite observar, por un lado, que la percepción del espacio urbano está basada en la fuerte identificación de los porteños con los barrios de la ciudad y, por otro lado, que existe en el imaginario colectivo una dicotomía norte-sur estilizada que se refleja tanto en lo social, lo espacial y lo lingüístico.

Kollektive Erinnerung. Topographie und Topik in Walthers ›Palästinalied‹

The French sociologist Maurice Halbwachs (1877–1945) conceived re- membrance as a product of ›collective memory‹ and explained this idea in his book on ›La Topographie légendaire des Évangiles en Terre sainte‹ (1941) showing that the topography of the Holy Land was predominantly an imaginary landscape construed by Christian communities. Following this concept, this article studies the ›Palästinalied‹, a text describing the arrival of a pilgrim in the Holy Land in the time of the crusades, abundantly transmitted under the name of Walther von der Vogelweide. The high degree of textual variance in the diverse manuscripts testifies the acting of ›collective memory‹ in the medieval poetic tradition. Of special interest in this context are the strophic arrangements, the variation of deictic markers, the reworking of melodic models documented in the manuscript transmission and the diatopic opposition existing between the emphasis of ›distant love‹ expressed in Jaufré Rudel’s Occitan song ›Lanqand li jorn son lonc en mai‹ (one of the named models) and the attitude of proximity prevailing in the ›Palästinalied‹.

The calculation of Afρ and mass loss rate for comets

Ab initio calculations of Afρ are presented using Mie scattering theory and a Direct Simulation Monte Carlo (DSMC) dust outflow model in support of the Rosetta mission and its target 67P/Churyumov-Gerasimenko (CG). These calculations are performed for particle sizes ranging from 0.010 μm to 1.0 cm. The present status of our knowledge of various differential particle size distributions is reviewed and a variety of particle size distributions is used to explore their effect on Afρ , and the dust mass production View the MathML sourcem˙. A new simple two parameter particle size distribution that curtails the effect of particles below 1 μm is developed. The contributions of all particle sizes are summed to get a resulting overall Afρ. The resultant Afρ could not easily be predicted a priori and turned out to be considerably more constraining regarding the mass loss rate than expected. It is found that a proper calculation of Afρ combined with a good Afρ measurement can constrain the dust/gas ratio in the coma of comets as well as other methods presently available. Phase curves of Afρ versus scattering angle are calculated and produce good agreement with observational data. The major conclusions of our calculations are: – The original definition of A in Afρ is problematical and Afρ should be: qsca(n,λ)×p(g)×f×ρqsca(n,λ)×p(g)×f×ρ. Nevertheless, we keep the present nomenclature of Afρ as a measured quantity for an ensemble of coma particles.– The ratio between Afρ and the dust mass loss rate View the MathML sourcem˙ is dominated by the particle size distribution. – For most particle size distributions presently in use, small particles in the range from 0.10 to 1.0 μm contribute a large fraction to Afρ. – Simplifying the calculation of Afρ by considering only large particles and approximating qsca does not represent a realistic model. Mie scattering theory or if necessary, more complex scattering calculations must be used. – For the commonly used particle size distribution, dn/da ∼ a−3.5 to a−4, there is a natural cut off in Afρ contribution for both small and large particles. – The scattering phase function must be taken into account for each particle size; otherwise the contribution of large particles can be over-estimated by a factor of 10. – Using an imaginary index of refraction of i = 0.10 does not produce sufficient backscattering to match observational data. – A mixture of dark particles with i ⩾ 0.10 and brighter silicate particles with i ⩽ 0.04 matches the observed phase curves quite well. – Using current observational constraints, we find the dust/gas mass-production ratio of CG at 1.3 AU is confined to a range of 0.03–0.5 with a reasonably likely value around 0.1.

New Myths of OZ: The Australian Beach and the Negotiation of National Belonging by Refugee Background Youth

In this article we consider the Australian beach as a material, imaginary and social arena in which different versions of national belonging are performed and contested. Focusing on two short films produced by young people from refugee backgrounds, we explore the negotiation of national belonging on the beach by people who occupy identity categories that are typically excluded from idealising Australian beach mythologies. We argue that both the production and distribution of these films contribute to a reimagining of the Australian beach that creates new opportunities for people from migrant backgrounds to engage in the co-production of Australian identities in their own terms.

Nonperturbative estimate of the heavy quark momentum diffusion coefficient

We estimate the momentum diffusion coefficient of a heavy quark within a pure SU(3) plasma at a temperature of about 1.5Tc. Large-scale Monte Carlo simulations on a series of lattices extending up to 1923×48 permit us to carry out a continuum extrapolation of the so-called color-electric imaginary-time correlator. The extrapolated correlator is analyzed with the help of theoretically motivated models for the corresponding spectral function. Evidence for a nonzero transport coefficient is found and, incorporating systematic uncertainties reflecting model assumptions, we obtain κ=(1.8–3.4)T3. This implies that the “drag coefficient,” characterizing the time scale at which heavy quarks adjust to hydrodynamic flow, is η−1D=(1.8–3.4)(Tc/T)2(M/1.5  GeV)  fm/c, where M is the heavy quark kinetic mass. The results apply to bottom and, with somewhat larger systematic uncertainties, to charm quarks.

«Einige Zeit aufs Singen verwendet». Musik als Kernressource dörflicher Kultur am Beispiel des schweizerischen 18. Jahrhunderts

Dealing with popular music in premodern times historical research usually focuses on so called “Volksmusik”. But already in the 18th century researchers were disappointed to find only few traces of imaginary “traditional” music in Switzerland. They unfortunately overlooked that common people kept on with their own stubborn musical culture: Beginning with the Reformation the authorities encouraged the communities to employ schoolmasters who were able to teach music. Their goal was that everybody should be able to participate in liturgical music actively. Over generations even people with no special musical talent adopted their own repertoire of psalms plus techniques of reading music and polyphonic singing. Spontaneous choral singing evolved into a common everyday practice. The most ambitious and brightest teachers even taught instrumental lessons at home on their proper pianos and chamber organs or encouraged the villagers to build new prestigious organs in their churches. The financial burden of such instruments weighted heavily on the communities. Some of them received financial support from the government, albeit unwillingly because it was obvious to the rulers that the villages just wanted to overtop each other. Homemade music was the most important issue in the cultural life of most parishes. Rich communes spent a lot of money to win the best voices on-site for their church choirs. Belonging to an elitists’ singer association paved the way to the farmer-village’s highlevel sociability.

PICADAR: a diagnostic predictive tool for primary ciliary dyskinesia.

Symptoms of primary ciliary dyskinesia (PCD) are nonspecific and guidance on whom to refer for testing is limited. Diagnostic tests for PCD are highly specialised, requiring expensive equipment and experienced PCD scientists. This study aims to develop a practical clinical diagnostic tool to identify patients requiring testing.Patients consecutively referred for testing were studied. Information readily obtained from patient history was correlated with diagnostic outcome. Using logistic regression, the predictive performance of the best model was tested by receiver operating characteristic curve analyses. The model was simplified into a practical tool (PICADAR) and externally validated in a second diagnostic centre.Of 641 referrals with a definitive diagnostic outcome, 75 (12%) were positive. PICADAR applies to patients with persistent wet cough and has seven predictive parameters: full-term gestation, neonatal chest symptoms, neonatal intensive care admittance, chronic rhinitis, ear symptoms, situs inversus and congenital cardiac defect. Sensitivity and specificity of the tool were 0.90 and 0.75 for a cut-off score of 5 points. Area under the curve for the internally and externally validated tool was 0.91 and 0.87, respectively.PICADAR represents a simple diagnostic clinical prediction rule with good accuracy and validity, ready for testing in respiratory centres referring to PCD centres.

Espacio, presencia, acontecimiento: configuración semántica de la existencia ficcional en un modelo teatral históricamente hegemónico

¿Qué implica para un personaje o para cualquier entidad habitante de un universo de ficción existir ficcionalmente? ¿Cuáles son los procedimientos que construyen esa existencia y cuáles sus consecuencias en el plano semántico? Mi contribución pretende responder esos interrogantes a partir de la demostración de la siguientes hipótesis: existe en el teatro un modelo tradicionalmente dominante de construcción de la existencia ficcional; los habitantes de un mundo ficcional adquieren su existencia, en ese modelo teatral hegemónico, mediante dos tipos de procedimientos semióticos: cualquier presencia inscripta en el espacio escénico y la autoridad legitimadora de existencia que tienen ciertos par-lamentos; la configuración semántica de la existencia ficcional no resulta sólo de los principios constructivos semióticos sino también de presuposiciones que pone en marcha el espectador a partir de sus hábitos interpretativos; la interacción entre procedimientos semióticos y operaciones activadas por el espectador genera, para esta clase de mundos ficcionales, una configuración semántica particular de la categoría de existencia.

Legitimidad religiosa y crisis social : estado, sociedad y expresiones religiosas en la Argentina del siglo XXI

Para entender la relación entre religión y política en Argentina, necesario reconocer las tendencias de justificación sagrada en los imaginarios religiosos. En este sentido, la legitimidad religiosa es construida sobre la crítica de la política neoliberal y sus consecuencias en la vida social (pobreza, exclusión, marginalidad). La presencia católica, las manifestaciones protestantes, y la crítica de otros grupos religiosos (por ejemplo, la crítica del rabino Alejandro Bloch) tienen en común una profunda objeción al neoliberalismo.

Espacios imaginarios en Tres tristes tigres de Guillermo Cabrera Infante

En Tres Tristes Tigres, una construcción metaficcional en la que las imágenes son la representación del recuerdo transfigurado por la imaginación, el espacio cumple una función peculiar. La Habana es el espacio imaginario, en los diversos momentos del día y en variados ámbitos y su figuración se apoya en la materia literaria, musical o fílmica incorporada al texto a través de diversos modos de alusión o de intertextualidad. En tanto que escritura, la página constituye también el espacio de resolución de la poética del juego.

Reconstruyendo imaginarios sobre democracia : a propósito de las elecciones a partir de la crisis del 2001

El trabajo aborda la relación democracia y ciudadanía desde la dimensión subjetiva de la política e indaga las representaciones mentales del imaginario político sobre participación y representación ciudadana a partir de los procesos electorales. El objetivo es rescatar las significaciones que sostienen o transforman la institucionalidad democrática. La crisis del 2001 en Argentina generó nuevas formas de participación y un redimensionamiento de la democracia. Los resultados del trabajo atribuyen la escasa calidad democrática a la dirigencia política aunque abren la posibilidad de un mayor compromiso, participación y autonomía ciudadana y recuperación de lo político, como inescindible de lo social.