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.

Lattice NRQCD study of in-medium bottomonium states using Nf = 2+1, 48³ × 12 HotQCD configurations

The behavior of bottomonium state correlators at non-zero temperature, 140.4(β = 6.664) ≤ T ≤ 221(β = 7.280) (MeV), where the transition temperature is 154(9) (MeV), is studied, using lattice NRQCD on 48³ ×12 HotQCD HiSQ action configurations with light dynamical Nf = 2+1 (mu,s/ms = 0.05) staggered quarks. In order to understand finite temperature effects on quarkonium states, zero temperature behavior of bottomonium correlators is compared based on 32⁴ (β = 6.664,6.800 and 6.950) and 48³ ×64 (β = 7.280) lattices. We find that temperature effects on S-wave bottomoniumstates are small but P-wave bottomoniumstates show a noticeable temperature dependence above the transition temperature.

Quantum Simulation of Non-Abelian Lattice Gauge Theories

We use quantum link models to construct a quantum simulator for U(N) and SU(N) lattice gauge theories. These models replace Wilson’s classical link variables by quantum link operators, reducing the link Hilbert space to a finite number of dimensions. We show how to embody these quantum link models with fermionic matter with ultracold alkaline-earth atoms using optical lattices. Unlike classical simulations, a quantum simulator does not suffer from sign problems and can thus address the corresponding dynamics in real time. Using exact diagonalization results we show that these systems share qualitative features with QCD, including chiral symmetry breaking and we study the expansion of a chirally restored region in space in real time.

Relation between Excitation Power Density and Er3+ Doping Yielding the Highest Absolute Upconversion Quantum Yield

The upconversion quantum yield (UCQY) is one of the most significant parameters for upconverter materials. A high UCQY is essential for a succesful integration of upconversion in many applications, such as harvesting of the solar radiation. However, little is known about which doping level of the rare-earth ions yields the highest UCQY in the different host lattices and what are the underlying causes. Here, we investigate which Er3+ doping yields the highest UCQY in the host lattices β-NaYF4 and Gd2O2S under 4I15/2 → 4I13/2 excitation. We show for both host lattices that the optimum Er3+ doping is not fixed and it actually decreases as the irradiance of the excitation increases. To find the optimum Er3+ doping for a given irradiance, we determined the peak position of the internal UCQY as a function of the average Er−Er distance. For this purpose, we used a fit on experimental data, where the average Er−Er distance was calculated from the Er3+ doping of the upconverter samples and the lattice parameters of the host materials. We observe optimum average Er−Er distances for the host lattices β-NaYF4 and Gd2O2S with differences <14% at the same irradiance levels, whereas the optimum Er3+ doping are around 2× higher for β-NaYF4 than for Gd2O2S. Estimations by extrapolation to higher irradiances indicate that the optimum average Er−Er distance converges to values around 0.88 and 0.83 nm for β-NaYF4 and Gd2O2S, respectively. Our findings point to a fundamental relationship and focusing on the average distance between the active rare-earth ions might be a very efficient way to optimize the doping of rare-earth ions with regard to the highest achievable UCQY.

Fairness

Die Fairnessnorm wird als eine der grundlegenden gesellschaftlichen Regeln für menschliches Entscheidungsverhalten betrachtet. Im folgenden Beitrag werden nach einer kurzen Einführung zunächst klassische moralphilosophische Auffassungen skizziert und grundlegende Vorstellungen über Gerechtigkeit und Fairness präsentiert. Dabei werden insbesondere distributive Fairnessprinzipien erläutert. Die empirische Evidenz zeigt, dass die Auswahl von Fairnessprinzipien und die Entscheidung, ob eine Fairnessnorm befolgt wird, kontextabhängig ist. Im Beitrag wird daher auch auf die Frage eingegangen, welche Motive von Akteuren ursächlich für die Befolgung einer Fairnessnorm sind. Es werden in diesem Zusammenhang Geltungsbedingungen und Entstehungsmechanismen für prosoziales Verhalten erörtert. Zur theoretischen Fundierung normorientierten Verhaltens wurden in den letzten beiden Dekaden Erweiterungen nutzentheoretischer Konzepte vorgeschlagen, die neben selbstinteressierten Präferenzen von Akteuren auch soziale Präferenzen berücksichtigen. Vorgestellt werden dabei nutzentheoretische Modelle, die sich mit egalitären Verteilungsprinzipien beschäftigen. Im Anschluss wird empirische Evidenz zur Fairnessnorm präsentiert, wobei insbesondere auf die Evidenz distributiver Fairnessprinzipien eingegangen wird und auf die Robustheit der Fairnessnorm im Rahmen experimenteller und feldexperimenteller Studien.

"Let's Talk Cash": Cantons' Interests and the Reform of Swiss Federalism

In 2004 the Swiss people accepted a new equalization scheme and a new distribution of competences between the federal state and the cantons. It was argued that the reform was successful because of the capacity of veto-players to overcome their interests and adopt a ‘problem-solving’ interaction mode. We propose a different interpretation and argue that distributive issues and the accommodation of actors' interests crucially mattered. We identify three mechanisms that contribute to a successful reform, i.e. package-deals, side-payments and the downsizing of the reform. Our in-depth, mainly qualitative study of both the content of the reform and related decision-making process supports the pertinence of these strategies for the explanation of the successful reform of Swiss federalism.

The Exploitation of Versatile Building Blocks for the Self-Assembly of Novel Molecular Magnets

Using molecular building blocks to self-assemble lattices supporting long-range magnetic order is currently an active area of solid-state chemistry. Consequently, it is the realm of supramolecular chemistry that synthetic chemists are turning to in order to develop techniques for the synthesis of structurally well-defined supramolecular materials. In recent years we have investigated the versatility and usefulness of two classes of molecular building blocks, namely, tris-oxalato transition-metal (M. Pilkington and S. Decurtins, in “Magnetoscience—From Molecules to Materials,” Wiley–VCH, 2000), and octacyanometalate complexes (Pilkington and Decurtins, Chimia 54, 593 (2001)), for applications in the field of molecule-based magnets. Anionic, tris-chelated oxalato building blocks are able to build up two-dimensional honeycomb-layered structural motifs as well as three-dimensional decagon frameworks. The discrimination between the crystallization of the two- or three-dimensional structures relies on the choice of the templating counterions (Decurtins, Chimia 52, 539 (1998); Decurtins et al. Mol. Cryst. Liq. Cryst. 273, 167 (1995); New J. Chem. 117 (1998)). These structural types display a range of ferro, ferri, and antiferromagnetic properties (Pilkington and Decurtins, in “Magnetoscience—From Molecules to Materials”). Octacyanometalate building blocks self-assemble to afford two new classes of cyano-bridged compounds namely, molecular clusters and extended three dimensional networks (J. Larionova et al., Angew. Chem. Int. Ed. 39, 1605 (2000); Pilkington et al., in preparation). The molecular cluster with a MnII9MoV6 core has the highest ground state spin value, S=51/2, reported to-date (Larionova et al., Angew. Chem. Int. Ed. 39, 1605 (2000)). In the high-temperature regime, the magnetic properties are characterized by ferromagnetic intracluster coupling. In the magnetic range below 44 K, the magnetic cluster signature is lost as possibly a bulk behavior starts to emerge. The three-dimensional networks exhibit both paramagnetic and ferromagnetic behavior, since the magnetic properties of these materials directly reflect the electronic configuration of the metal ion incorporated into the octacyanometalate building blocks (Pilkington et al., in preparation). For both the oxalate- and cyanide-bridged materials, we are able to manipulate the magnetic properties of the supramolecular assemblies by tuning the electronic configurations of the metal ions incorporated into the appropriate molecular building blocks (Pilkington and Decurtins, in “Magnetoscience—From Molecules to Materials,” Chimia 54, 593 (2000)).

Numerical corrections to the strong coupling effective Polyakov-line action for finite T Yang-Mills theory

We consider a three-dimensional effective theory of Polyakov lines derived previously from lattice Yang-Mills theory and QCD by means of a resummed strong coupling expansion. The effective theory is useful for investigations of the phase structure, with a sign problem mild enough to allow simulations also at finite density. In this work we present a numerical method to determine improved values for the effective couplings directly from correlators of 4d Yang-Mills theory. For values of the gauge coupling up to the vicinity of the phase transition, the dominant short range effective coupling are well described by their corresponding strong coupling series. We provide numerical results also for the longer range interactions, Polyakov lines in higher representations as well as four-point interactions, and discuss the growing significance of non-local contributions as the lattice gets finer. Within this approach the critical Yang-Mills coupling β c is reproduced to better than one percent from a one-coupling effective theory on N τ = 4 lattices while up to five couplings are needed on N τ = 8 for the same accuracy.

Skolemization for Substructural Logics

The usual Skolemization procedure, which removes strong quantifiers by introducing new function symbols, is in general unsound for first-order substructural logics defined based on classes of complete residuated lattices. However, it is shown here (following similar ideas of Baaz and Iemhoff for first-order intermediate logics in [1]) that first-order substructural logics with a semantics satisfying certain witnessing conditions admit a “parallel” Skolemization procedure where a strong quantifier is removed by introducing a finite disjunction or conjunction (as appropriate) of formulas with multiple new function symbols. These logics typically lack equivalent prenex forms. Also, semantic consequence does not in general reduce to satisfiability. The Skolemization theorems presented here therefore take various forms, applying to the left or right of the consequence relation, and to all formulas or only prenex formulas.

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.

La dimensión moral en el marxismo : la justicia distributiva en Marx y en los marxistas analíticos

El artículo aborda la dimensión moral en el marxismo desde el enunciado del concepto de justicia distributiva. La existencia explícita o implícita de una dimensión moral en el marxismo ha sido discutida en la bibliografía, sobre todo a partir del análisis de los propios textos de Marx. El artículo afirma la existencia de una noción transhistórica y absoluta de justicia en Marx y en el grupo de los marxistas analíticos, aunque en éstos últimos con distintas variantes.

Lectura de Marx : tras el concepto de clases sociales

A pesar de que toda la teoría de Marx tiene por centro y corazón la lucha de clases, Marx no formuló con la sistematicidad que se ocupó de otros temas una «Teoría» de las clases sociales, en tanto sistema de conceptos rigurosamente definidos. El propósito de este artículo es recomponer algunas cuestiones centrales en la definición marxista de las clases sociales, así como demostrar la enorme significación teórica del descubrimiento de Marx. Se pretende por último señalar la distancia respecto de toda concepción subjetivista, economicista, voluntarista, distributiva y socio-profesional de las clases.

El ataque libertarista contra el igualitarismo y el marxismo : actualidad de un debate inconcluso

El presente artículo examina las principales líneas de ataque lanzadas por el libertarismo de derecha -expresado fundamentalmente en la obra de Robert Nozick-, contra el igualitarismo liberal de John Rawls y el materialismo histórico. En particular, analiza el rechazo nozickeano a la justicia distributiva, a la deseabilidad (y posibilidad) de la cooperación social, y a los esquemas distributivos contrarios al principio de autopropiedad. Asimismo, explora el impacto de este principio libertarista sobre algunos postulados fundamentales del marxismo. Desde una perspectiva que se nutre de los principales debates de la filosofía política contemporánea, y con una opción teórica por el igualitarismo, este texto presenta y procura debilitar las más audaces tesis nozickeanas, las cuales siguen ejerciendo gran influencia en círculos académicos, en algunas instancias de formulación de políticas públicas y, sobre todo, en el sentido común forjado en tiempos de hegemonía neoliberal.

Estado, sociedad y medios de comunicación : contribuciones para pensar la política

El trabajo tiene el propósito de indagar, en la teoría social latinoamericana, la relación entre Estado, sociedad y medios de comunicación. Aunque esta intención expresa un carácter eminentemente teórico se sustenta en la intrincada e ineludible relación entre teoría y realidad social. Relación que nos lleva a preguntarnos por la concreción de las prácticas políticas hoy vigentes. Esto implica re-pensar no solamente los modelos de Estado en pugna, que van desde la intervención pro-cíclica y distributiva a los que lo definen como mero reproductor de la explotación y la desigualdad, sino también por las distintas concepciones de individuo-sociedad que trasvasan dichos modelos y el rol que dichos modelos le asignan a los medios de comunicación. Se trata, entonces, de rescatar los aportes que se construyeron desde los enfoques del desarrollismo y la dependencia, por entenderlos válidos y pertinentes para analizar la realidad actual de nuestro continente. Ciertamente, muchos de los problemas estructurales actuales de las sociedades capitalistas latinoamericanas se pueden pensar a la luz de esos aportes que comenzaron a construirse en la década de los ´60. La noción de desarrollo, con distintas variantes, no sólo es una constante en el pensamiento latinoamericano sino que atraviesa la política contemporánea.

La acción pública en el espacio urbano : debates y reflexiones en torno a la noción de política urbana

En este artículo se propone reflexionar sobre un conjunto de herramientas conceptuales que permitan analizar los modos en los cuales se configura la acción pública en el espacio urbano. Para ello se revisan una serie de contribuciones de la teoría política que consideran al aparato burocrático, en tanto objetivación de las instituciones estatales, como garante de las relaciones de producción hegemónicas. Y, al mismo tiempo, se supone que el ámbito intraestatal posee una dinámica específica, constituyéndose como un espacio de disputa política entre diversos actores. Teniendo en cuenta este escenario, el análisis de las políticas públicas implica una lectura dinámica acerca de la articulación de las relaciones sociales en el ámbito estatal, que exige indagar las estrategias y los intereses de los actores que se organizan en torno a redes o entramados según las cuestiones socialmente problematizadas que logran permear la agenda pública. Desde esta perspectiva se propone elaborar una definición de política urbana y delimitar una serie de interrogantes básicos para su abordaje. Para tal fin, se consideran ciertas particularidades que asume la política urbana como una política pública de fuerte impronta territorial. Además, se reconocen distintas formas de intervención estatal en el espacio urbano y ciertos nudos problemáticos que hacen a la definición de la cuestión urbana en la actualidad, escenario de la sanción de un nuevo marco normativo en la provincia de Buenos Aires.