Cooper pairing with finite angular momentum: BCS versus Bose limits

We revisit the old problem of exotic superconductivity as Cooper pairing with finite angular momentum emerging from a central potential. Based on some general considerations, we suggest that the phenomenon is associated with interactions that keep electrons at some particular, finite distance r(0), and occurs at a range of intermediate densities n similar to 1/r(0)(3). We discuss the ground state and the critical temperature in the framework of a standard functional-integral theory of the BCS to Bose crossover. We find that, due to the lower energy of two-body bound states with l = 0, the rotational symmetry of the ground state is always restored on approaching the Bose limit. Moreover in that limit the critical temperature is always higher for pairs with l = 0. The breaking of the rotational symmetry of the continuum by the superfluid state thus seems to be a property of weakly-attractive, non-monotonic interaction potentials, at intermediate densities

Condensation in an Economic Model with Brand Competition

We present a linear agent based model on brand competition. Each agent belongs to one of the two brands and interacts with its nearest neighbors. In the process the agent can decide to change to the other brand if the move is beneficial. The numerical simulations show that the systems always condenses into a state when all agents belong to a single brand. We study the condensation times for different parameters of the model and the influence of different mechanisms to avoid condensation, like anti monopoly rules and brand fidelity.Comment: Accepted in: International Journal of Modern Physics

Broken time-reversal symmetry probed by muon spin relaxation in the caged type superconductor Lu5Rh6Sn18

The superconducting state of the caged type compound Lu5Rh6Sn18 has been investigated by using magnetization, heat capacity, and muon spin relaxation or rotation (?SR) measurements, and the results interpreted on the basis of the group theoretical classifications of the possible pairing symmetries and a simple model of the resulting quasiparticle spectra. Our zero-field ?SR measurements clearly reveal the spontaneous appearance of an internal magnetic field below the transition temperature, which indicates that the superconducting state in this material is characterized by broken time-reversal symmetry. Further, the analysis of the temperature dependence of the magnetic penetration depth measured using the transverse-field ?SR measurements suggests an isotropic s?wave character for the superconducting gap. This is in agreement with the heat capacity behavior, and we show that it can be interpreted in terms of a nonunitary triplet state with point nodes and an open Fermi surface

Ultracold Gases of Ytterbium: Ferromagnetism and Mott States in an SU(6) Fermi System

It is argued that ultracold quantum degenerate gas of ytterbium $^{173}$Yb atoms having nuclear spin $I = 5/2$ exhibits an enlarged SU$(6)$ symmetry. Within the Landau Fermi liquid theory, stability criteria against Fermi liquid (Pomeranchuk) instabilities in the spin channel are considered. Focusing on the SU$(n > 2)$ generalizations of ferromagnetism, it is shown within mean-field theory that the transition from the paramagnet to the itinerant ferromagnet is generically first order. On symmetry grounds, general SU$(n)$ itinerant ferromagnetic ground states and their topological excitations are also discussed. These SU$(n > 2)$ ferromagnets can become stable by increasing the scattering length using optical methods or in an optical lattice. However, in an optical lattice at current experimental temperatures, Mott states with different filling are expected to coexist in the same trap, as obtained from a calculation based on the SU$(6)$ Hubbard model.Comment: 4+ pages, 1 figure; v2: Improved discussion of the SU(6) symmetry-breaking patterns; v3: added further discussion on the order of the transition. Added Reference

Uso de un sistema para la gestión del aprendizaje (LMS) de código libre en la Universidad Tecnológica del Suroeste de Guanajuato (UTSOE)

The use of the Information and Communication Technologies (ICT) in Learning Environment allows achieving the maximum interaction between Teachers and Students.The Virtual Learning Environments are computer programs that benefit the learning facilitating the communication between users. Open Source software allow to create the own online modular learning environment with a fast placed in service. In the present paper the use of a Learning Management Systems (LMS) as continuous education tool is proposed

Examining the California Cut Score: An Empirical Analysis of Minimum Competency, Public Protection, Disparate Impact, and National Standards

The selection of a minimum bar exam passing score (“cut score”) shapes the representation of racial and ethnic minorities in the legal profession and the quality of access to justice in the state. California and national policy makers have not had the benefit of detailed exam performance data that analyzes the effect of the cut score on race and ethnicity. Because policy makers consider the cut score an important public protection mechanism, this study also explored whether the selection of higher cut scores better protected the public from attorneys who do not have the minimum competence to practice law. To conduct the analysis, the study used two data sets. The first data set included 85,727 examinees who sat for 21 administrations of the CBX from 2009-18 and the race and ethnicity of each examinee. The second data set included the ABA discipline data from up to 48 U.S. jurisdictions from 2013-18 and the cut scores in each jurisdiction. Using the first data set,the study determined how the selection of a minimum cut score (1) widens or narrows the racial and ethnic impacts of the bar exam and/or (2) alters the racial and ethnic composition of new attorneys joining the legal profession. Both historical actual and simulated cut scores were analyzed. Using the second data set, this study examined a third factor: the relationship, if any, between minimum cut scores and rates of attorney discipline. This analysis determined that initial and eventual passing rates differed significantly between racial and ethnic groups, and this gap was wider at higher simulated cut scores. A simulation analysis using actual examinee scores confirmed that selecting a lower cut score would have significantly narrowed the achievement gap between Whites and racial and ethnic minorities and would have increased the number of newly admitted minority attorneys in California. For example, at 1440, the achievement gap between Whites and Blacks was 27.4 percentage points. But at a simulated cut score of 1300, the achievement gap between these two groups would have been only 14.5 percentage points. This 12.9 percentage point difference in the achievement gap at 1440 and 1300 demonstrates a disparate effect of the higher cut scores. Using the second data set about disciplinary statistics, the study determined that no relationship exists between the selection of a cut score and the number of complaints, formal charges, or disciplinary actions taken against attorneys in the jurisdictions studied. California’s recent decision to lower the cut score from 1440 to 1390 moved California from having the second-highest cut score to the fourth-highest cut score in the country. However, the report data established that at 1390 California will continue to produce significantly disparate pass rates on the basis of race and ethnicity when compared to the national norm of 1350, the New York standard of 1330, and the simulated model of 1300. This study establishes that maintaining a high cut score does not result in greater public protection as measured by disciplinary statistics but does result in excluding minorities from admission to the bar and the practice of law at rates disproportionately higher than Whites

Extended States in a One-dimensional Generalized Dimer Model

The transmission coefficient for a one dimensional system is given in terms of Chebyshev polynomials using the tight-binding model. This result is applied to a system composed of two impurities located between $N$ sites of a host lattice. It is found that the system has extended states for several values of the energy. Analytical expressions are given for the impurity site energy in terms of the electron's energy. The number of resonant states grows like the number of host sites between the impurities. This property makes the system interesting since it is a simple task to design a configuration with resonant energy very close to the Fermi level $E_F$.Comment: 4 pages, 3 figure

Layerless fabrication with continuous liquid interface production

Despite the increasing popularity of 3D printing, also known as additive manufacturing (AM), the technique has not developed beyond the realm of rapid prototyping. This confinement of the field can be attributed to the inherent flaws of layer-by-layer printing and, in particular, anisotropic mechanical properties that depend on print direction, visible by the staircasing surface finish effect. Continuous liquid interface production (CLIP) is an alternative approach to AM that capitalizes on the fundamental principle of oxygen-inhibited photopolymerization to generate a continual liquid interface of uncured resin between the growing part and the exposure window. This interface eliminates the necessity of an iterative layer-by-layer process, allowing for continuous production. Herein we report the advantages of continuous production, specifically the fabrication of layerless parts. These advantages enable the fabrication of large overhangs without the use of supports, reduction of the staircasing effect without compromising fabrication time, and isotropic mechanical properties. Combined, these advantages result in multiple indicators of layerless and monolithic fabrication using CLIP technology

Cartografía de malas hierbas en cultivos de maíz mediante imágenes hiperespectrales aeroportadas (AHS)

El presente trabajo aborda la cartografía de las malas hierbas Sorghum halepense, Xanthium strumarium y Abutilon theophrasti en cultivos de maíz mediante técnicas de teledetección hiperespectral. Se ha utilizado una imagen adquirida por el sensor aeroportado AHS (Airborne Hyperspectral Scanner) con una resolución espacial en el nadir de 2,5 m y 80 bandas espectrales desde 0,43 hasta 12,5µm. La imagen fue adquirida en mayo de 2007, coincidiendo con el momento óptimo para la aplicación del herbicida, sobre una zona cultivada de maíz en la finca experimental La Poveda situada al SE de la Comunidad de Madrid. Se aplicaron diversas correcciones geométricas y radiométricas, incluida la conversión a reflectividades, que se llevó a cabo mediante un ajuste empírico basado en mediciones espectrales realizadas sobre el terreno simultáneamente a la adquisición de la imagen. La técnica de Análisis de Mezclas Espectrales (ALME) nos permitió obtener un mapa de cobertura de cada una de las malas hierbas analizadas así como información sobre las proporciones de cada cubierta (malas hierbas y maíz/suelo) en cada píxel. La validación realizada para la especie S. halepense utilizando como referencia los perímetros de los rodales obtenidos con GPS mostró que sólo un 16,8 % de la superficie ocupada por esta especie no fue discriminada a partir de la imagen.El presente trabajo ha sido realizado en el marco del proyecto “Ecología espacio-temporal y teledetección de malas hierbas en cultivos de maíz” AGL2005-06180-C03-01 financiado por el Ministerio de Ciencia e Innovación.Peer reviewe

Fermi surface instabilities at finite Temperature

We present a new method to detect Fermi surface instabilities for interacting systems at finite temperature. We first apply it to a list of cases studied previously, recovering already known results in a very economic way, and obtaining most of the information on the phase diagram analytically. As an example, in the continuum limit we obtain the critical temperature as an implicit function of the magnetic field and the chemical potential $T_c(\mu,h)$. By applying the method to a model proposed to describe reentrant behavior in $Sr_3Ru_2O_7$, we reproduce the phase diagram obtained experimentally and show the presence of a non-Fermi Liquid region at temperatures above the nematic phase.Comment: 10 pages, 10 figure