Non-Hermitian Boundary Modes

We consider conditions for the existence of boundary modes in non-Hermitian systems with edges of arbitrary co-dimension. Through a universal formulation of formation criteria for boundary modes in terms of local Green functions, we outline a generic perspective on the appearance of such modes and generate corresponding dispersion relations. In the process, we explain the skin effect in both topological and non-topological systems, exhaustively generalizing bulk-boundary correspondence in the presence of non-Hermiticity. This is accomplished via a doubled Green's function, inspired by doubled Hamiltonian methods used to classify Floquet and, more recently, non-Hermitian topological phases. Our work constitutes a general tool, as well as, a unifying perspective for this rapidly evolving field. Indeed, as a concrete application we find that our method can expose novel non-Hermitian topological regimes beyond the reach of previous methods.Comment: 15 pages, 4 figures. Supplement added. Substantial extension of result

Localization via Quasi-Periodic Bulk-Bulk Correspondence

We report on a direct connection between quasi-periodic topology and the Almost Mathieu (Andre-Aubry) metal insulator transition (MIT). By constructing quasi-periodic transfer matrix equations from the limit of rational approximate projected Green's functions, we relate results from $\text{SL}(2,\mathbb{R})$ co-cycle theory (transfer matrix eigenvalue scaling) to consequences of rational band theory. This reduction links the eigenfunction localization of the MIT to the chiral edge modes of the Hofstadter Hamiltonian, implying the localized phase roots in a topological "bulk-bulk" correspondence, a bulk-boundary correspondence between the 1D AAH system (boundary) and its 2D parent Hamiltonian (bulk). This differentiates quasi-periodic localization from Anderson localization in disordered systems. Our results are widely applicable to systems beyond this paradigmatic model.Comment: 6+12 pages, 2+2 figures, 1 table. Companion paper to arXiv:2109.13933 concerning different themes and new results. Supplementary materials shared with arXiv:2109.13933, but kept for readability and completeness. arXiv admin note: substantial text overlap with arXiv:2109.1393

Legislación Político-lingüística

English Teacher Education Programs reflect different political, pedagogical and epistemological positions, as well as language ideologies. These specific ideologies can be approached through the study of language policies in the field of sociology of language. The purpose of the present work is to explore how sociolinguistic representations and ideologies are embodied in the 1999 and 2019 texts of the English Teacher Education Programs of a state-owned university in Mar del Plata, Argentina. To that end, discourse analysis methodology will be used to identify different subjective stances.Los planes de estudios de carreras de formación docente en idiomas, además de reflejar distintos tipos de posiciones políticas, pedagógicas y epistemológicas, concretan ideologías y representaciones acerca de las lenguas. Estas pueden ser abordadas a partir del estudio de las políticas lingüísticas desde el seno de la sociología del lenguaje. El propósito del presente trabajo es dilucidar las formas en que dos de los conceptos vinculados a las políticas lingüísticas, i.e., las representaciones sociolingüísticas y las ideologías, operaron en la redacción de los Planes de Estudios del Profesorado de Inglés de 1999 y 2019 en una universidad estatal de la ciudad de Mar del Plata, Argentina. A tal fin, rastreamos el corpus propuesto mediante metodología del análisis del discurso para identificar distintas formaciones subjetivas

The red-bellied squirrel in Argentina and the management of introduced species as a biological and social problem

El estudio y manejo de especies exóticas invasoras ha estado principalmente enfocado en conocer el proceso de invasión y técnicas adecuadas de manejo. Sin embargo, en los últimos años los estudios que promueven la participación de diferentes grupos sociales de la comunidad en los planes de manejo han cobrado importancia. En este trabajo describimos las opiniones y actitudes predominantes de seis grupos sociales (productores y prestadores de servicios, ambientalistas, vecinos, personal de áreas protegidas, funcionarios y docentes) con respecto a la presencia de la ardilla de vientre rojo introducida en Argentina. La existencia de varios focos de invasión de ardillas en tres provincias argentinas se relaciona con liberaciones intencionales de ardillas, en ocasiones obtenidas por comercio ilegal. Las opiniones con respecto a la presencia de ardillas variaron desde una percepción negativa que consideraba que era una especie problema que debía ser controlada hasta una percepción positiva que sostiene que es una especie atractiva y vistosa. Algunos grupos mostraron una opinión predominante, mientras que otros reflejaron todo el rango de respuestas. La experiencia directa con la especie, sus atributos y el tiempo desde su introducción, el área de residencia y el grado de conocimiento sobre la problemática influyen sobre las opiniones y actitudes de las personas. Las alternativas de manejo deben planificarse para cada zona invadida teniendo en cuenta las particularidades no sólo biológicas y económicas, sino también sociales y políticas. Al mismo tiempo, resulta imprescindible una  estrategia nacional de prevención para frenar la aparición de nuevos focos de invasión. Para esto es fundamental desarrollar estrategias que reorienten la relación de las personas con los recursos del ambiente y promuevan la valoración de los ecosistemas locales y especies nativas, así como la co-responsabilidad y la participación ciudadana en la problemática de las invasiones biológicas, el tráfico de fauna y la tenencia de mascotas.The study and management of exotic invasive species has been mainly focused on understanding the invasion process and designing adequate management techniques; however, in recent years several studies have shown the importance of involving social groups of the local community in the implementation of management plans. In this study we describe opinions and attitudes of six social groups (producers and service providers, environmentalists, neighbours, personnel of protected areas, civil servants, and teachers) regarding the presence of the red-bellied squirrels introduced in Argentina. The occurrence of various invasion foci of squirrels in three Argentinian provinces results from intentional releases of individuals, sometimes obtained by illegal trade. Opinion towards the presence of squirrels ranged from a negative perception of the squirrels viewed as a problem species that needs to be controlled to a positive perception of the squirrels viewed as an attractive species. Some groups showed a predominant opinion while others reflected the whole range of responses. Personal experience with the species, its attributes and the time since its introduction, the area of residency, and the knowledge of the problems posed by this species affect the opinion and attitudes towards the presence of red-bellied squirrels. Management plans must be designed for each invasion focus not only considering biological and economic issues, but also social and political ones. At the same time, a national strategy of prevention to stop the creation of new invasion foci is urgently needed. We therefore need strategies to reorient the relationship between people and environmental resources and to promote appreciation of local ecosystems and native species as much as co-responsibility and citizen participation in the problems posed by biological invasions, and the illegal trade of wild fauna and pets.Fil: Borgnia, Mariela. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Benitez, Verónica Victoria. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Gozzi, Cecilia. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Guichon, Maria Laura. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentin

Where do Models go Wrong? Parameter-Space Saliency Maps for Explainability

Conventional saliency maps highlight input features to which neural network predictions are highly sensitive. We take a different approach to saliency, in which we identify and analyze the network parameters, rather than inputs, which are responsible for erroneous decisions. We find that samples which cause similar parameters to malfunction are semantically similar. We also show that pruning the most salient parameters for a wrongly classified sample often improves model behavior. Furthermore, fine-tuning a small number of the most salient parameters on a single sample results in error correction on other samples that are misclassified for similar reasons. Based on our parameter saliency method, we also introduce an input-space saliency technique that reveals how image features cause specific network components to malfunction. Further, we rigorously validate the meaningfulness of our saliency maps on both the dataset and case-study levels

Canary in a Coalmine: Better Membership Inference with Ensembled Adversarial Queries

As industrial applications are increasingly automated by machine learning models, enforcing personal data ownership and intellectual property rights requires tracing training data back to their rightful owners. Membership inference algorithms approach this problem by using statistical techniques to discern whether a target sample was included in a model's training set. However, existing methods only utilize the unaltered target sample or simple augmentations of the target to compute statistics. Such a sparse sampling of the model's behavior carries little information, leading to poor inference capabilities. In this work, we use adversarial tools to directly optimize for queries that are discriminative and diverse. Our improvements achieve significantly more accurate membership inference than existing methods, especially in offline scenarios and in the low false-positive regime which is critical in legal settings. Code is available at https://github.com/YuxinWenRick/canary-in-a-coalmine.Comment: Code is available at https://github.com/YuxinWenRick/canary-in-a-coalmine, published as a conference paper at ICLR 202

The Augmented Lagrange Multiplier Method for Exact Recovery of Corrupted Low-Rank Matrices

This paper proposes scalable and fast algorithms for solving the Robust PCA problem, namely recovering a low-rank matrix with an unknown fraction of its entries being arbitrarily corrupted. This problem arises in many applications, such as image processing, web data ranking, and bioinformatic data analysis. It was recently shown that under surprisingly broad conditions, the Robust PCA problem can be exactly solved via convex optimization that minimizes a combination of the nuclear norm and the $\ell^1$-norm . In this paper, we apply the method of augmented Lagrange multipliers (ALM) to solve this convex program. As the objective function is non-smooth, we show how to extend the classical analysis of ALM to such new objective functions and prove the optimality of the proposed algorithms and characterize their convergence rate. Empirically, the proposed new algorithms can be more than five times faster than the previous state-of-the-art algorithms for Robust PCA, such as the accelerated proximal gradient (APG) algorithm. Moreover, the new algorithms achieve higher precision, yet being less storage/memory demanding. We also show that the ALM technique can be used to solve the (related but somewhat simpler) matrix completion problem and obtain rather promising results too. We further prove the necessary and sufficient condition for the inexact ALM to converge globally. Matlab code of all algorithms discussed are available at http://perception.csl.illinois.edu/matrix-rank/home.htmlComment: Please cite "Zhouchen Lin, Risheng Liu, and Zhixun Su, Linearized Alternating Direction Method with Adaptive Penalty for Low Rank Representation, NIPS 2011." (available at arXiv:1109.0367) instead for a more general method called Linearized Alternating Direction Method This manuscript first appeared as University of Illinois at Urbana-Champaign technical report #UILU-ENG-09-2215 in October 2009 Zhouchen Lin, Risheng Liu, and Zhixun Su, Linearized Alternating Direction Method with Adaptive Penalty for Low Rank Representation, NIPS 2011. (available at http://arxiv.org/abs/1109.0367

El rol del laboratorio de virología en la pandemia de COVID-19: Diagnóstico de SARS-CoV-2

Desde el inicio de la pandemia de COVID-19, el Laboratorio deVirología del Hospital Garrahan, implementó el diagnóstico molecular de SARS-CoV-2 mediante RT-PCR para dar respuestarápida y de calidad a la creciente demanda. Al diagnóstico pediátrico se sumó el diagnóstico de los padres / acompañantes ypersonal de salud con criterio de caso sospechoso. Al inicio del2021 se incorporó el test rápido de detección de antígeno parapacientes sintomáticos. Hasta junio de 2021 se procesó un totalde 58 000 muestras para estudios moleculares.Since the beginning of the COVID-19 pandemic, the Virology Laboratory of Garrahan Hospital has implemented molecular diagnosis of SARS-CoV-2 using RT-PCR in order to provide a rapid and high-quality response to the growing demand. In addition to the pediatric diagnosis, the diagnosis of parents/companions and healthcare personnel meeting the criteria of a suspected case was also added. At the beginning of 2021, the rapid antigen detection test for symptomatic patients was incorporated. Until June 2021, a total of 58,000 samples were analyzed by molecular studies.Fil: Borgnia, Daniela. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Rios, Daniela Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Mangano, Andrea María Mercedes. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin