Majorana fermions in superconducting wires: Effects of long-range hopping, broken time-reversal symmetry, and potential landscapes

We present a comprehensive study of two of the most experimentally relevant extensions of Kitaev's spinless model of a one-dimensional p-wave superconductor: those involving (i) longer-range hopping and superconductivity and (ii) inhomogeneous potentials. We commence with a pedagogical review of the spinless model and, as a means of characterizing topological phases exhibited by the systems studied here, we introduce bulk topological invariants as well as those derived from an explicit consideration of boundary modes. In time-reversal symmetric systems, we find that the longer range hopping leads to topological phases characterized by multiple Majorana modes. In particular, we investigate a spin model that respects a duality and maps to a fermionic model with multiple Majorana modes; we highlight the connection between these topological phases and the broken symmetry phases in the original spin model. In the presence of time-reversal symmetry breaking terms, we show that the topological phase diagram is characterized by an extended gapless regime. For the case of inhomogeneous potentials, we explore phase diagrams of periodic, quasiperiodic, and disordered systems. We present a detailed mapping between normal state localization properties of such systems and the topological phases of the corresponding superconducting systems. This powerful tool allows us to leverage the analyses of Hofstadter's butterfly and the vast literature on Anderson localization to the question of Majorana modes in superconducting quasiperiodic and disordered systems, respectively. We briefly touch upon the synergistic effects that can be expected in cases where long-range hopping and disorder are both present.

CTFS-ForestGEO: a worldwide network monitoring forests in an era of global change

Global change is impacting forests worldwide, threatening biodiversity and ecosystem services including climate regulation. Understanding how forests respond is critical to forest conservation and climate protection. This review describes an international network of 59 long-term forest dynamics research sites (CTFS-ForestGEO) useful for characterizing forest responses to global change. Within very large plots (median size 25ha), all stems 1cm diameter are identified to species, mapped, and regularly recensused according to standardized protocols. CTFS-ForestGEO spans 25 degrees S-61 degrees N latitude, is generally representative of the range of bioclimatic, edaphic, and topographic conditions experienced by forests worldwide, and is the only forest monitoring network that applies a standardized protocol to each of the world's major forest biomes. Supplementary standardized measurements at subsets of the sites provide additional information on plants, animals, and ecosystem and environmental variables. CTFS-ForestGEO sites are experiencing multifaceted anthropogenic global change pressures including warming (average 0.61 degrees C), changes in precipitation (up to +/- 30% change), atmospheric deposition of nitrogen and sulfur compounds (up to 3.8g Nm(-2)yr(-1) and 3.1g Sm(-2)yr(-1)), and forest fragmentation in the surrounding landscape (up to 88% reduced tree cover within 5km). The broad suite of measurements made at CTFS-ForestGEO sites makes it possible to investigate the complex ways in which global change is impacting forest dynamics. Ongoing research across the CTFS-ForestGEO network is yielding insights into how and why the forests are changing, and continued monitoring will provide vital contributions to understanding worldwide forest diversity and dynamics in an era of global change.

Scanning gate microscopy of current-annealed single layer graphene

We have used scanning gate microscopy to explore the local conductivity of a current-annealed graphene flake. A map of the local neutrality point (NP) after annealing at low current density exhibits micron-sized inhomogeneities. Broadening of the local e-h transition is also correlated with the inhomogeneity of the NP. Annealing at higher current density reduces the NP inhomogeneity, but we still observe some asymmetry in the e-h conduction. We attribute this to a hole-doped domain close to one of the metal contacts combined with underlying striations in the local NP. © 2010 American Institute of Physics.

Letras, 1998, nº 37 (número completo)

Contenido: Federico García Lorca en Buenos Aires: una entrevista y un artículo olvidados / Andrew Anderson – Metáforas de la Argentina / Gloria Videla de Rivero – El resumen de textos de carácter académico / Hilda Albano de Vázquez – Hecho de Estampas, de Jacobo Fijman: poetización de un proceso / María Amelia Arancet Ruda – La ideología profética del Palmerín de Oliva / Javier Roberto González – La vanguardia teatral de los años 20 en la obra de Vicente Martínez Cuitiño /Luis Martínez Cuitiño – Coincidencias temáticas en la narrativa contemporánea hispanoamericana y croata: ejemplos de relación entre la nueva historia y la novela / Mirjana Polic Bobic – “Gantasi, Monte Aldín, Daganel y Galdenda, topónimos del Amadís de Gaula” / Aquilino Suárez Pallasá – Literatura de viajes y teatro comparado / Jorge Dubatti – Reseñas bibliográficas

Anuario Argentino de Derecho Canónico, 1998, Vol. V (número completo)

Contenido: Abreviaturas y citas – Artículos: Los sacramentales de la Iglesia, el matrimonio y la familia / J. Bonet Alcón – Los consejos de asuntos económicos / A. W. Bunge – I beni culturali di interesse religioso in Italia : la collaborazione tra autorità ecclesiastiche e autorità civil / G. Feliciani – El Opus Dei y sus tribunales / C. I. Heredia – Errore e simulazione circa la sacramentalità del matrimonio nella realtà dell’odierna società postcristiana / M. F. Pompedda – Notas – Jurisprudencia – Actualidad – Legislación particular argentina -- Recensiones

Las tensiones de la idea de la justicia de Amartya Sen

Resumen: En este artículo, se ensaya un análisis crítico del libro de Amartya Sen La idea de la justicia. En primer lugar, se analizan los contrastes entre pragmatismo y objetividad en la idea de justicia propuesta por Sen. Luego se desarrolla el concepto de ‘capacidad’ propuesto por este economista, y se presentan las objeciones de Martha Nussbaum a este planteo. A continuación, el artículo señala los vínculos entre la idea de justicia y las concepciones económicas de Amartya Sen y analiza el debate acerca del esquema de maximización protagonizado por este pensador y Elizabeth Anderson. Finalmente, se realiza una valoración de la obra como totalidad, destacando la importancia de la razón práctica en el análisis de la justicia.