G20: ¿declina?

La reciente cumbre del Grupo de los Veinte (G20) se vio afectada por la guerra de Ucrania. No podía ser de otra manera dado el impacto que ese conflicto ha llegado a tener en la escena internacional. En este caso, en las deliberaciones y actividades de pasillo, hubo una fuerte condena a la actuación rusa por parte de una mayoría de los países integrantes del Grupo. Se reflejó en la declaración final al deplorar “en los términos más enérgicos la agresión de la Federación de Rusia contra Ucrania” y exigir su retirada total e incondicional de ese territorio. En la cumbre la víctima principal fue el consenso. Así, la necesidad de sacar la declaración dio lugar a la mención de que “hubo otros puntos de vista y diferentes evaluaciones de la situación y las sanciones”. Se aludía de esa manera un tanto forzada a la posición rusa y la de otros países que no fueron tan tajantes en la condena. En sintonía con sus bases conceptuales, el G20 debe operar en forma consensuada. A fin del siglo pasado cuando el G7 decide su nacimiento, en las primeras definiciones se decía que “el Grupo convoca a dialogar y construir consenso para impulsar políticas públicas que resuelvan los desafíos que enfrenta la humanidad”. Ese principio se mantuvo luego de que comenzaran a funcionar las cumbres de líderes en 2008. El primero que rompió la regla fue el presidente de los EE.UU., Donald Trump en Alemania en 2017 cuando propuso abandonar el Acuerdo de París en contra de la opinión de los otros 19 miembros, un desacuerdo que fue reflejado en la Declaración Final. El otro caso se dio ahora en la cumbre de Bali donde, obviamente, Rusia se opuso a condenar el papel que le era endilgado por sus pares, a pesar de lo cual, la Declaración Final, también con las debidas salvedades, no dejó de salir. En ambos casos se daba la paradoja de que en el consenso estaba contenido el disenso. Malabares de los magos de la diplomacia cuando tienen que redactar un párrafo indigerible para una de las partes, la que sin embargo no quiere dejar de firmar para no quedar afuera o aguarle la fiesta al dueño de casa. Sea como sea, en el G20 las fisuras ya están expuestas.Instituto de Relaciones Internacionale

Variaciones y efectos del experimentalismo democrático

Hay otra historia de teorías y prácticas sociales que presentan alternativas a la visión restringida de la democracia representativa. Que sostienen que la democracia es una forma de vida basada en la afirmación de la igualdad de las personas, la importancia del diálogo libre y la actividad para concretar efectivamente las decisiones. Que no entienden que la representación excluya la presencia política directa, ni que los procedimientos regulados sean más importantes que lo que posibilitan. Que muestran que las complejidades técnicas de los asuntos públicos pueden trabajarse colectivamente en la medida en que se generen los contextos adecuados. Que hablan públicamente de problemas silenciados, que invitan a la acción alegre, que desarrollan soluciones creativas y efectivas. Estas teorías y prácticas alternativas responden así a la denuncia del déficit democrático y la crisis de representación con un fuerte experimentalismo, que busca extender y profundizar la igualdad y la libertad reales en el estado y la sociedad, pasando de una democracia restringida a una democracia participativa. En este artículo quiero destacar unas pocas cuestiones que actores de experiencias democráticas en Rosario, Argentina, vinculan a la participación directa y luego remarcar algunos de sus efectos, que muestran que la democracia no necesariamente tiene que ser chata, aburrida ni irrelevante

A Geometrically Supported z∼10z\sim10 Candidate Multiply-Imaged by the Hubble Frontier Fields Cluster Abell 2744

The deflection angles of lensed sources increase with their distance behind a given lens. We utilize this geometric effect to corroborate the $z_{phot}\simeq9.8$ photometric redshift estimate of a faint near-IR dropout, triply-imaged by the massive galaxy cluster Abell 2744 in deep Hubble Frontier Fields images. The multiple images of this source follow the same symmetry as other nearby sets of multiple images which bracket the critical curves and have well defined redshifts (up to $z_{spec}\simeq3.6$), but with larger deflection angles, indicating that this source must lie at a higher redshift. Similarly, our different parametric and non-parametric lens models all require this object be at $z\gtrsim4$, with at least 95\% confidence, thoroughly excluding the possibility of lower-redshift interlopers. To study the properties of this source we correct the two brighter images for their magnifications, leading to a SFR of $\sim0.3 M_{\odot}$/yr, a stellar mass of $\sim4\times10^{7} M_{\odot}$, and an age of $\lesssim220$ Myr (95\% confidence). The intrinsic apparent magnitude is 29.9 AB (F160W), and the rest-frame UV ($\sim1500 \AA$) absolute magnitude is $M_{UV,AB}=-17.6$. This corresponds to $\sim0.1 L^{*}_{z=8}$ ($\sim0.2 L^{*}_{z=10}$, adopting $dM^{*}/dz\sim0.45$), making this candidate one of the least luminous galaxies discovered at $z\sim10$.Comment: 7 pages, 4 figures, 1 table; V2: very minor changes, ApJ Letters Accepte

Boosting mobility performance with multi-path TCP

Proceeding of: Future Network & Mobile Summit 2010, 16 - 18 June 2010, Florence, ItalyFourth Generation mobile devices incorporate multiple interfaces with diverse access technologies. The current Mobile IP protocol fails to support the enhanced fault tolerance capabilities that are enabled by the availability of multiple interfaces. In particular, established Mobile IP communications cannot be preserved through outages affecting the Home Address. In this paper we describe an architecture for mobile host multihoming that enables transport layer survivability through multiple failure modes. The proposed approach relies on the cooperation between Mobile IP and Multi-Path TCP and aims to fully support multihoming and extend roaming capabilities of mobile devices.This research was supported by Trilogy (http://www.trilogy-project.org), a research project (ICT-216372) partially funded by the European Community under its Seventh Framework Programme.European Community's Seventh Framework ProgramNo publicad

A Novel Training Program to Improve Human Spatial Orientation: Preliminary Findings

The ability to form a mental representation of the surroundings is a critical skill for spatial navigation and orientation in humans. Such a mental representation is known as a "cognitive map" and is formed as individuals familiarize themselves with the surrounding, providing detailed information about salient environmental landmarks and their spatial relationships. Despite evidence of the malleability and potential for training spatial orientation skills in humans, it remains unknown if the specific ability to form cognitive maps can be improved by an appositely developed training program. Here, we present a newly developed computerized 12-days training program in a virtual environment designed specifically to stimulate the acquisition of this important skill. We asked 15 healthy volunteers to complete the training program and perform a comprehensive spatial behavioral assessment before and after the training. We asked participants to become familiar with the environment by navigating a small area before slowly building them up to navigate within the larger and more complex environment; we asked them to travel back and forth between environmental landmarks until they had built an understanding of where those landmarks resided with respect to one another. This process repeated until participants had visited every landmark in the virtual town and had learned where each landmark resided with respect to the others. The results of this study confirmed the feasibility of the training program and suggested an improvement in the ability of participants to form mental representations of the spatial surrounding. This study provides preliminary findings on the feasibility of a 12-days program in training spatial orientation skills. We discuss the utility and potential impact of this training program in the lives of the many individuals affected by topographical disorientation as a result of an acquired or developmental condition

Radio Interferometric Planet Search II: Constraints on sub-Jupiter-Mass Companions to GJ 896A

We present results from the Radio Interferometric Planet (RIPL) search for compan- ions to the nearby star GJ 896A. We present 11 observations over 4.9 years. Fitting astrometric parameters to the data reveals a residual with peak-to-peak amplitude of ~ 3 mas in right ascension. This residual is well-fit by an acceleration term of 0.458 \pm 0.032 mas/y^2. The parallax is fit to an accuracy of 0.2 mas and the proper motion terms are fit to accuracies of 0.01 mas/y. After fitting astrometric and acceleration terms residuals are 0.26 mas in each coordinate, demonstrating that stellar jitter does not limit the ability to carry out radio astrometric planet detection and characterization. The acceleration term originates in part from the companion GJ 896B but the amplitude of the acceleration in declination is not accurately predicted by the orbital model. The acceleration sets a mass upper limit of 0.15 MJ at a semi-major axis of 2 AU for a planetary companion to GJ 896A. For semi-major axes between 0.3 and 2 AU upper limits are determined by the maximum angular separation; the upper limits scale from the minimum value in proportion to the inverse of the radius. Upper limits at larger radii are set by the acceleration and scale as the radius squared. An improved solution for the stellar binary system could improve the exoplanet mass sensitivity by an order of magnitude.Comment: Accepted for publication in Ap

CLASH: Weak-Lensing Shear-and-Magnification Analysis of 20 Galaxy Clusters

We present a joint shear-and-magnification weak-lensing analysis of a sample of 16 X-ray-regular and 4 high-magnification galaxy clusters at 0.19<z<0.69 selected from the Cluster Lensing And Supernova survey with Hubble (CLASH). Our analysis uses wide-field multi-color imaging, taken primarily with Suprime-Cam on the Subaru Telescope. From a stacked shear-only analysis of the X-ray-selected subsample, we detect the ensemble-averaged lensing signal with a total signal-to-noise ratio of ~25 in the radial range of 200 to 3500kpc/h. The stacked tangential-shear signal is well described by a family of standard density profiles predicted for dark-matter-dominated halos in gravitational equilibrium, namely the Navarro-Frenk-White (NFW), truncated variants of NFW, and Einasto models. For the NFW model, we measure a mean concentration of $c_{200c}=4.01^{+0.35}_{-0.32}$ at $M_{200c}=1.34^{+0.10}_{-0.09} 10^{15}M_{\odot}$. We show this is in excellent agreement with Lambda cold-dark-matter (LCDM) predictions when the CLASH X-ray selection function and projection effects are taken into account. The best-fit Einasto shape parameter is $\alpha_E=0.191^{+0.071}_{-0.068}$, which is consistent with the NFW-equivalent Einasto parameter of $\sim 0.18$. We reconstruct projected mass density profiles of all CLASH clusters from a joint likelihood analysis of shear-and-magnification data, and measure cluster masses at several characteristic radii. We also derive an ensemble-averaged total projected mass profile of the X-ray-selected subsample by stacking their individual mass profiles. The stacked total mass profile, constrained by the shear+magnification data, is shown to be consistent with our shear-based halo-model predictions including the effects of surrounding large-scale structure as a two-halo term, establishing further consistency in the context of the LCDM model.Comment: Accepted by ApJ on 11 August 2014. Textual changes to improve clarity (e.g., Sec.3.2.2 "Number-count Depletion", Sec.4.3 "Shape Measurement", Sec.4.4 "Background Galaxy Selection"). Results and conclusions remain unchanged. For the public release of Subaru data, see http://archive.stsci.edu/prepds/clash

Hamiltonian Dynamics and the Phase Transition of the XY Model

A Hamiltonian dynamics is defined for the XY model by adding a kinetic energy term. Thermodynamical properties (total energy, magnetization, vorticity) derived from microcanonical simulations of this model are found to be in agreement with canonical Monte-Carlo results in the explored temperature region. The behavior of the magnetization and the energy as functions of the temperature are thoroughly investigated, taking into account finite size effects. By representing the spin field as a superposition of random phased waves, we derive a nonlinear dispersion relation whose solutions allow the computation of thermodynamical quantities, which agree quantitatively with those obtained in numerical experiments, up to temperatures close to the transition. At low temperatures the propagation of phonons is the dominant phenomenon, while above the phase transition the system splits into ordered domains separated by interfaces populated by topological defects. In the high temperature phase, spins rotate, and an analogy with an Ising-like system can be established, leading to a theoretical prediction of the critical temperature $T_{KT}\approx 0.855$.Comment: 10 figures, Revte