Failure of single-parameter scaling of wave functions in Anderson localization

We show how to use properties of the vectors which are iterated in the transfer-matrix approach to Anderson localization, in order to generate the statistical distribution of electronic wavefunction amplitudes at arbitary distances from the origin of $L^{d-1} \times \infty$ disordered systems. For $d=1$ our approach is shown to reproduce exact diagonalization results available in the literature. In $d=2$, where strips of width $L \leq 64$ sites were used, attempted fits of gaussian (log-normal) forms to the wavefunction amplitude distributions result in effective localization lengths growing with distance, contrary to the prediction from single-parameter scaling theory. We also show that the distributions possess a negative skewness $S$, which is invariant under the usual histogram-collapse rescaling, and whose absolute value increases with distance. We find $0.15 \lesssim -S \lesssim 0.30$ for the range of parameters used in our study, .Comment: RevTeX 4, 6 pages, 4 eps figures. Phys. Rev. B (final version, to be published

Susceptibility and Percolation in 2D Random Field Ising Magnets

The ground state structure of the two-dimensional random field Ising magnet is studied using exact numerical calculations. First we show that the ferromagnetism, which exists for small system sizes, vanishes with a large excitation at a random field strength dependent length scale. This {\it break-up length scale} $L_b$ scales exponentially with the squared random field, $\exp(A/\Delta^2)$. By adding an external field $H$ we then study the susceptibility in the ground state. If $L>L_b$, domains melt continuously and the magnetization has a smooth behavior, independent of system size, and the susceptibility decays as $L^{-2}$. We define a random field strength dependent critical external field value $\pm H_c(\Delta)$, for the up and down spins to form a percolation type of spanning cluster. The percolation transition is in the standard short-range correlated percolation universality class. The mass of the spanning cluster increases with decreasing $\Delta$ and the critical external field approaches zero for vanishing random field strength, implying the critical field scaling (for Gaussian disorder) $H_c \sim (\Delta -\Delta_c)^\delta$, where $\Delta_c = 1.65 \pm 0.05$ and $\delta=2.05\pm 0.10$. Below $\Delta_c$ the systems should percolate even when H=0. This implies that even for H=0 above $L_b$ the domains can be fractal at low random fields, such that the largest domain spans the system at low random field strength values and its mass has the fractal dimension of standard percolation $D_f = 91/48$. The structure of the spanning clusters is studied by defining {\it red clusters}, in analogy to the ``red sites'' of ordinary site-percolation. The size of red clusters defines an extra length scale, independent of $L$.Comment: 17 pages, 28 figures, accepted for publication in Phys. Rev.

Analytic Trajectories for Mobility Edges in the Anderson Model

A basis of Bloch waves, distorted locally by the random potential, is introduced for electrons in the Anderson model. Matrix elements of the Hamiltonian between these distorted waves are averages over infinite numbers of independent site-energies, and so take definite values rather than distributions of values. The transformed Hamiltonian is ordered, and may be interpreted as an itinerant electron interacting with a spin on each site. In this new basis, the distinction between extended and localized states is clear, and edges of the bands of extended states, the mobility edges, are calculated as a function of disorder. In two dimensions these edges have been found in both analytic and numerical applications of tridiagonalization, but they have not been found in analytic approaches based on perturbation theory, or the single-parameter scaling hypothesis; nor have they been detected in numerical approaches based on scaling or critical distributions of level spacing. In both two and three dimensions the mobility edges in this work are found to separate with increasing disorder for all disorders, in contrast with the results of calculation using numerical scaling for three dimensions. The analytic trajectories are compared with recent results of numerical tridiagonalization on samples of over 10^9 sites. This representation of the Anderson model as an ordered interacting system implies that in addition to transitions at mobility edges, the Anderson model contains weaker transitions characterized by critical disorders where the band of extended states decouples from individual sites; and that singularities in the distribution of site energies, rather than its second moment, determine localization properties of the Anderson model.Comment: 32 pages, 2 figure

The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment

The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since July 2014. This paper describes the second data release from this phase, and the fourteenth from SDSS overall (making this, Data Release Fourteen or DR14). This release makes public data taken by SDSS-IV in its first two years of operation (July 2014-2016). Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey (eBOSS); the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data driven machine learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS website (www.sdss.org) has been updated for this release, and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020, and will be followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14 happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov 2017 (this is the "post-print" and "post-proofs" version; minor corrections only from v1, and most of errors found in proofs corrected

Soccer and homosexuality: the conflicts that lie within the affective game of the coach-adolescent athlete relationship

Discussions regarding homosexuality within a sports context are mediated by emotional nuances, especially in the world of soccer, where practitioners are required to have attributes such as strength, masculinity and aggressiveness. As a consequence, this work aimed to analyze the symbolic representation of homosexual relationships between adolescent soccer players and their coaches; and, furthermore, to understand the intention behind homoerotic relationships that are established between members of the management team and its players. In this study, researchers used the life history methodology, with participation from three adolescent athletes, ages 14, 15 and 16, and three former athletes, ages 26, 28 and 45, who we called speakers. Based on the collection and analysis of research participants’ testimonies, homosexual relations were found to have occurred between athletes and coaches, or between athletes and other members of the management team, as a part of a “social contract” that is exclusively linked to their professional objectives. These relationships appear to be purely objective; authentic affective links are absent, due apparently to the transient nature of the athletes in these groups. Too, this context is usually marked by the athlete’s physical and emotional vulnerability, and the agreements he makes within this context are accompanied with moral dilemmas, because such adolescents idealize the coach as a paternal archetype.“Futebol e homossexualidade: Os conflitos que se encontram dentro do jogo afetivo da relação treinador-atleta adolescente.” As discussões a respeito da homossexualidade no contexto esportivo são mediadas por nuanças emocionais, especialmente no mundo do futebol que exige de seus praticantes atributos de força, virilidade e agressividade. Por este motivo este trabalho teve como objetivos diagnosticar existência de relações homossexuais entre atletas adolescentes da modalidade de futebol e seus técnicos e sua representação simbólica e ainda, compreender a intencionalidade das relações homoafetivas que se estabelecem entre componentes da equipe diretiva e os jogadores. Esta pesquisa é de natureza qualitativa e a técnica adotada foi a “história de vida” e a participação de três atletas adolescentes em atividade, com idade de 14, 15 e 16 anos e três ex-atletas profissionais, com idades 26, 28 e 45 anos serviram de base metodológica. A partir da análise e tratamento dos depoimentos verificou-se que ocorreram relações homossexuais nas categorias de base envolvendo técnico e atleta, ou com outros membros da equipe diretiva, como parte dos contratos sociais, ligados exclusivamente a objetivos profissionais. Estas relações parecem ser puramente objetais, não parecendo existir vínculos afetivos duradouros, aparentemente, devido à natureza transitória de atletas nesses grupos. Também, nesses ambientes, muitas vezes marcados pela vulnerabilidade física e emocional dos atletas, os acertos para as relações homossexuais são permeadas por dilemas morais, tendo em vista que os atletas adolescentes idealizam o treinador como o arquétipo paterno ideal.“El fútbol y la homosexualidad: Los conflictos que se encuentran dentro del juego afectivo de la relación atleta-entrenador de los adolescentes.” Las discusiones sobre la homosexualidad en contexto deportivo están mediadas por matices emocionales, sobre todo en el mundo del fútbol que exige a sus jugadores atributos como la fuerza, la virilidad y los jugadores. En este estudio, los investigadores utilizaron la metodología de la historia de vida, con la participación de tres atletas adolescentes, con 14, 15 y 16 años, y tres ex atletas con 26, 28 y 45 años, que llamamos ‘oradores’. Basado en la recogida y análisis de testimonios de participantes en la investigación, se encontró que las relaciones homosexuales que se han producido entre los atletas y entrenadores, o entre atletas y otros miembros del equipo de gestión, son como parte de un “contrato social” que está vinculado exclusivamente a sus objetivos profesionales. Estas relaciones parecen ser solamente como un objeto; porque a veces no hay vínculos afectivos auténticos, debido aparentemente a la naturaleza transitoria de los atletas en estos grupos. Demasiado, este contexto es generalmente marcado por la vulnerabilidad física y emocional del deportista, y los acuerdos que hace dentro de este contexto se acompañan con dilemas morales, debido a que tales adolescentes idealizan el entrenador como un arquetipo paterno. la agresividad. Por lo tanto, este estudio tuvo como objetivo diagnosticar la existencia de relaciones homosexuales entre adolescentes atletas de fútbol y sus entrenadores y la representación simbólica de estas relaciones. También comprender la intencionalidad de las relaciones homoafetivas que se intercambian entre algunos componentes del equipo directivo y(undefined

Search for gamma-ray emission from DES dwarf spheroidal galaxy candidates with Fermi-LAT data

Due to their proximity, high dark-matter (DM) content, and apparent absence of non-thermal processes, Milky Way dwarf spheroidal satellite galaxies (dSphs) are excellent targets for the indirect detection of DM. Recently, eight new dSph candidates were discovered using the first year of data from the Dark Energy Survey (DES). We searched for gamma-ray emission coincident with the positions of these new objects in six years of Fermi Large Area Telescope data. We found no significant excesses of gamma-ray emission. Under the assumption that the DES candidates are dSphs with DM halo properties similar to the known dSphs, we computed individual and combined limits on the velocity-averaged DM annihilation cross section for these new targets. If the estimated DM content of these dSph candidates is confirmed, they will constrain the annihilation cross section to lie below the thermal relic cross section for DM particles with masses ≲ 20 {GeV} annihilating via the b\bar{b} or tau+tau- channels

Do Frogs Get Their Kicks on Route 66? Continental U.S. Transect Reveals Spatial and Temporal Patterns of Batrachochytrium dendrobatidis Infection

The chytrid fungus Batrachochytrium dendrobatidis (Bd) has been devastating amphibians globally. Two general scenarios have been proposed for the nature and spread of this pathogen: Bd is an epidemic, spreading as a wave and wiping out individuals, populations, and species in its path; and Bd is endemic, widespread throughout many geographic regions on every continent except Antarctica. To explore these hypotheses, we conducted a transcontinental transect of United States Department of Defense (DoD) installations along U.S. Highway 66 from California to central Illinois, and continuing eastward to the Atlantic Seaboard along U.S. Interstate 64 (in sum from Marine Corps Base Camp Pendleton in California to Naval Air Station Oceana in Virginia). We addressed the following questions: 1) Does Bd occur in amphibian populations on protected DoD environments? 2) Is there a temporal pattern to the presence of Bd? 3) Is there a spatial pattern to the presence of Bd? and 4) In these limited human-traffic areas, is Bd acting as an epidemic (i.e., with evidence of recent introduction and/or die-offs due to chytridiomycosis), or as an endemic (present without clinical signs of disease)? Bd was detected on 13 of the 15 bases sampled. Samples from 30 amphibian species were collected (10% of known United States' species); half (15) tested Bd positive. There was a strong temporal (seasonal) component; in total, 78.5% of all positive samples came in the first (spring/early-summer) sampling period. There was also a strong spatial component—the eleven temperate DoD installations had higher prevalences of Bd infection (20.8%) than the four arid (<60 mm annual precipitation) bases (8.5%). These data support the conclusion that Bd is now widespread, and promote the idea that Bd can today be considered endemic across much of North America, extending from coast-to-coast, with the exception of remote pockets of naïve populations

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio