Coulomb Drag between One-Dimensional Wigner Crystal Rings

We consider the Coulomb drag between two metal rings in which the long range Coulomb interaction leads to the formation of a Wigner crystal. The first ring is threaded by an Ahranov Bohm flux creating a persistent current J_0. The second ring is brought in close proximity to the second and due to the Coulomb interaction between the two rings a drag current J_D is produced in the second. We investigate this system at zero temperature for perfect rings as well as the effects of impurities. We show that the Wigner crystal state can in principle lead to a higher ratio of drag current to drive current J_D/J_0 than in weakly interacting electron systems.Comment: 12 pages, 10 figure

A Tonks Giradeau Gas in the Presence of a Local Potential

The physics of a Tonks-Giradeau Gas in the presence of a local potential is studied. In order to evaluate the single particle density matrix (SPDM) of the many-body ground state, the Wiger-Jordan transformation is used. The eigenvector with the largest eigenvalue of the SPDM corresponds to the "Bose-Einstein Condensate"(BEC) State. We find that the "BEC" state density at the positon of the local potential decreases, as expected, in the case of a repulsive potential. For an attractive potential, it decreases or increases depending on the strength of the potential. The superfluidity of this system is investigated both numerically and perturbatively. An experimental method for detecting the effect of an impurity in a Tonks-Giradueau gas is discussed.Comment: 14 pages, 5 figure

Microscopic origin of granular ratcheting

Numerical simulations of assemblies of grains under cyclic loading exhibit ``granular ratcheting'': a small net deformation occurs with each cycle, leading to a linear accumulation of deformation with cycle number. We show that this is due to a curious property of the most frequently used models of the particle-particle interaction: namely, that the potential energy stored in contacts is path-dependent. There exist closed paths that change the stored energy, even if the particles remain in contact and do not slide. An alternative method for calculating the tangential force removes granular ratcheting.Comment: 13 pages, 18 figure

La revista‘ Materiales de Construcción’, 2003-2012: un análisis bibliométrico

The aim of the present work was to make a bibliometric analysis of research articles and technical notes published in the journal ‘Materiales de Construcción’ between 2003 and 2012. Authors’ productivity and collaboration, affiliation and nationality of authors, collaboration amongst institutions using techniques of social networks analysis, and the impact factor of the journal were analyzed. The results show high levels in authors’ diversification and collaboration; high number of institutions but a low level of collaboration among them; and a big increase of impact factor during all the period. The main conclusion of this work is that ‘Materiales de Construcción’ has evolved positively since 2003 to 2012, becoming a quality journal in its area.El objetivo del presente trabajo es realizar un análisis bibliométrico de los artículos y notas técnicas que se han publicado en la revista Materiales de Construcción entre 2003 y 2012. Se analizan la productividad de los autores y el grado de colaboración entre los mismos, las instituciones de los autores y sus países de origen, la colaboración entre las instituciones de autores utilizando técnicas de análisis de redes sociales y el factor de impacto de la revista. Los resultados indican que hay elevados niveles en la diversificación y en la colaboración de autores; un alto número de instituciones pero un escaso grado de colaboración entre las mismas; y un gran incremento en el factor de impacto durante el periodo analizado. La principal conclusión de este trabajo es que Materiales de Construcción ha evolucionado positivamente desde 2003 a 2012, llegando a ser una revista de calidad en su ámbito

"Universal" resistance jump of vortices at the melting transition

We consider the jump in resistance at the melting transition, which is experimentally observed to be constant, independent of magnetic field (vortex density). We present an explanation of this effect based on vortex cuttings, and universalities of the structure factor at the freezing transition (the Hansen-Verlet criterion)

Tunneling edges at strong disorder

Scattering between edge states that bound one-dimensional domains of opposite potential or flux is studied, in the presence of strong potential or flux disorder. A mobility edge is found as a function of disorder and energy, and we have characterized the extended phase. "paper_FINAL.tex" 439 lines, 20366 characters In the presence of flux and/or potential disorder, the localization length scales exponentially with the width of the barrier. We discuss implications for the random-flux problem.Comment: RevTeX, 4 page

A library of near-infrared integral field spectra of young M-L dwarfs

We present a library of near-infrared (1.1-2.45 microns) medium-resolution (R~1500-2000) integral field spectra of 15 young M6-L0 dwarfs, composed of companions with known ages and of isolated objects. We use it to (re)derive the NIR spectral types, luminosities and physical parameters of the targets, and to test (BT-SETTL, DRIFT-PHOENIX) atmospheric models. We derive infrared spectral types L0+-1, L0+-1, M9.5+-0.5, M9.5+-0.5, M9.25+-0.25, M8+0.5-0.75, and M8.5+-0.5 for AB Pic b, Cha J110913-773444, USco CTIO 108B, GSC 08047-00232 B, DH Tau B, CT Cha b, and HR7329B, respectively. BT-SETTL and DRIFT-PHOENIX models yield close Teff and log g estimates for each sources. The models seem to evidence a 600-300+600 K drop of the effective temperature at the M-L transition. Assuming the former temperatures are correct, we derive new mass estimates which confirm that DH Tau B, USco CTIO 108B, AB Pic b, KPNO Tau 4, OTS 44, and Cha1109 lay inside or at the boundary of the planetary mass range. We combine the empirical luminosities of the M9.5-L0 sources to the Teff to derive semi-empirical radii estimates that do not match "hot-start" evolutionary models predictions at 1-3 Myr. We use complementary data to demonstrate that atmospheric models are able to reproduce the combined optical and infrared spectral energy distribution, together with the near-infrared spectra of these sources simultaneously. But the models still fail to represent the dominant features in the optical. This issue casts doubts on the ability of these models to predict correct effective temperatures from near-infrared spectra alone. We advocate the use of photometric and spectroscopic data covering a broad range of wavelengths to study the properties of very low mass young companions to be detected with the planet imagers (Subaru/SCExAO, LBT/LMIRCam, Gemini/GPI, VLT/SPHERE).Comment: 27 pages, 14 tables, 19 figures, accepted for publication in Astronomy & Astrophysic