One-dimensional topological insulators in the AIII symmetry class

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica. Fecha de lectura: 23-10-2019Esta tesis tiene embargado el acceso al texto completo hasta el 23-04-2021En este trabajo proponemos un modelo de aislante topológico unidimensional en la clase de simetría AIII, la cual no ha sido realizada experimentalmente. Analizamos los estados de borde del modelo y encontramos dos propiedades interesantes. Por un lado, el momento de los estados de borde puede estar bien definido, adicionalmente a su buena localización espacial en los extremos del sistema. Por otro lado, el momento de los estados de borde es diferente de cero en la clase de simetría AIII. La presencia de simetría de inversión temporal en la clase BDI hace que los estados de borde tengan momento cero. Por lo tanto, los estados de borde con momento diferente de cero constituyen una propiedad característica de la clase de simetría AIII. En consecuencia de las propiedades del momento de los estados de borde, el fenómeno de fraccionalización también tiene lugar en el espacio de momentos. Diseñamos un procedimiento experimental para realizar el modelo utilizando átomos fríos en redes ópticas y mostramos cómo la clase de simetría AIII abre una nueva posibilidad para la detección de fenómeno de fraccionalización en aislantes topológicos unidimensionales. Además, diseñamos un protocolo de quench en el que los estados de borde se desplazan a lo largo del sistema manteniendo su identidad de cuasipartículas fraccionalizadas e interfieren entre sí. Por otra parte, extendemos nuestro estudio de aislantes topológicos unidimensionales y consideramos modelos de escalera. Llevamos a cabo un análisis detallado de modelos topológicos de escalera y concluimos que estos pueden ser clasificados en seis tipos diferentes, los cuales están caracterizados por una configuración de fermiones de Wilson distinta. Mostramos cómo cualquier modelo topológico de escalera puede ser obtenido mediante la aplicación de una transformación unitaria a un modelo de escalera particular, el cual, por tanto, sirve de modelo canónico. Utilizamos este modelo de escalera canónico para obtener la función de onda de los estados de borde de cualquier modelo topológico de escalera y analizar sus propiedades. De este modo vemos que los estados de borde de un modelo topológico de escalera están estrechamente relacionados con los fermiones de Wilson que dicho modelo describe. Cada fermión de Wilson se corresponde con una componente de momento en la función de onda de los estados de borde, cuyo peso relativo viene dado por la masa del fermión asociado. Como resultado, cada uno de los seis diferentes tipos de modelos topológicos de escalera da lugar a un tipo distinto de estados de borde, los cuales están caracterizados mediante su distribución de densidad en el espacio de momentos. Adicionalmente proporcionamos una lista con todas las geometría de escalera particulares que dan lugar a un modelo topológico. Por último, analizamos en mayor detalle uno de ellos y diseñamos un protocolo de quench que da lugar a corrientes quirales protegidas. Esta corrientes son el resultado de las propiedades de localización de los estados de borde en el espacio de posiciones y el de momentos, junto con la presencia de un flujo magnético efectivo que rompe la simetría de inversión temporalIn this work we propose a model for a one-dimensional topological insulator in the AIII symmetry class, which lacks experimental realization. We analyse the edge states of the model and find two interesting properties. On one hand, the momentum of the edge states can be well defined, in addition to their good spacial localization at the edges of the system. On the other hand, the edge states momentum is different from zero in the AIII class. The presence of time reversal symmetry in the BDI class makes the edge states have a zero momentum. Thus, edge states with a non-zero momentum is a characteristic property of the AIII class. As a consequence of the edge states momentum properties, the phenomenon of fractionalization also occurs in momentum space. We design an experimental procedure to realize the model using cold atoms in optical lattices and show how the AIII class opens a new possibility for the detection of the phenomenon of fractionalization in one-dimensional topological insulators. Furthermore, we design a quench protocol in which the edge states travel along the system keeping their identity of fractionalized quasiparticles and interfere with each other. Besides that, we extend our study of one-dimensional topological insulators and consider ladder models. We make a detailed analysis of topological ladders and conclude that all topological ladder models can be classified into six different types, which are characterized by a different configuration of Wilson fermions. We show how every topological ladder model can be obtained by applying a unitary transformation onto a particular ladder geometry, which thus serves as a canonical ladder model. We use this canonical ladder to obtain the wave function of the edge states of a general topological ladder model and analyse their properties. In this way, we show how the edge states of a topological ladder are closely related to the Wilson fermions described by the model. Each Wilson fermion corresponds to a different momentum component in the edge states wave function, being their relative weights determined by the mass of the associated fermion. As a result, each of the six different types of topological ladder models gives rise to a distinct type of edge states, which are characterized by their momentum density distribution. Finally, we provide a list with all particular ladder geometries that correspond to a topological insulator. Moreover, we analyse in more detail one of them and design a quench protocol that results in the emergence of protected chiral currents. These currents are the consequence of the spatial and momentum localizations of the edge states and the presence of an effective magnetic field that breaks time reversal symmetryThis research was funded by the grant BES-2013-064443 of the Spanish MINECO, as well as by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) via Research Unit FOR 2414 under project number 27797465

Labour flexibility and productivity in the hotel sector

In this paper, we analyze the effect of labour flexibility on productivity in the Andalusian hotel industry using raw data of our own database and applying an expanded version of the standard production function by distinguishing between part-time, temporary, and full-time labour inputs. Our results show that productivity is lower the higher the percentage of temporary and part-time workers and there are no differences between the impacts on productivity of both types of labour contract. Future studies should analyze the differential impact of all the types of contracts discussed on the mean cost per employee in this sector.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Situational-Context: A Unified View of Everything Involved at a Particular Situation

As the interest in the Web of Things increases, specially for the general population, the barriers to entry for the use of these technologies should decrease. Current applications can be developed to adapt their behaviour to predefined conditions and users preferences, facilitating their use. In the future,Web of Things software should be able to automatically adjust its behaviour to non-predefined preferences or context of its users. In this vision paper we define the Situational-Context as the combination of the virtual profiles of the entities (things or people) that concur at a particular place and time. The computation of the Situational-Context allow us to predict the expected system behaviour and the required interaction between devices to meet the entities’ goals, achieving a better adjustment of the system to variable contexts.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Frequency domain minimum distance inference for possibly noninvertible and noncausal arma models.

This article introduces frequency domain minimum distance procedures for performing inference in general, possibly non causal and/or noninvertible, autoregressive moving average (ARMA) models. We use information from higher order moments to achieve identification on the location of the roots of the AR and MA polynomials for non-Gaussian time series. We propose a minimum distance estimator that optimally combines the information contained in second, third, and fourth moments. Contrary to existing estimators, the proposed one is consistent under general assumptions, and may improve on the efficiency of estimators based on only second order moments. Our procedures are also applicable for processes for which either the third or the fourth order spectral density is the zero function.Supported by Ministerio Economía y Competitividad (Spain), Grants ECO2012-31748, ECO2014-57007p and MDM 2014-0431, and Comunidad de Madrid, MadEco-CM (S2015/HUM- 3444). Supported by Asociación Mexicana de Cultura and from the Mexican Consejo Nacional de Ciencia y Tecnología (CONACYT) under project Grant 151624

Los asentamientos rurales en Cantabria. Propuesta de clasificación según el tipo de planta.

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Generación de conocimiento tecnológico y políticas de innovación : dimensiones e interrelaciones

Existen diferencias significativas en la evolución de la competitividad y el progreso tecnológico en el contexto internacional. Ello se puede explicar en gran medida por la desigual estructura de los Sistemas Nacionales de Inno-vación de los países cuyo estudio constituye el principal objetivo del presente artículo. Para su consecución, proponemos y seguiremos un marco de análisis integrado por cuatro dimensiones básicas de los sistemas de innovación: ad-ministraciones públicas, interacción sistema público de I+D-industria/compor-tamiento empresarial, sistema de financiación y movilidad de personal/sistema de educación. Cada una de ellas representa elementos clave para explicar la intensidad de generación y flujo de conocimiento tecnológico entre los agen-tes implicados en los procesos de innovación, determinando la tasa y dirección del aprendizaje tecnológico. ____________________________________________There are prominent differences in the evolution of the competitiveness and technological progress in the international context. This is a consequence of a dissimilar structure of National Systems of Innovation, which analysis is the main aim of this paper. For this purpose, we propose and take into account an analysis framework that is built up by four dimensions: public administra-tions, interaction between public system of R&D and industry/entrepreneurial behavior, finance system and mobility of skill labor/education system. Each dimension represents a key factor to explain the intensity of the technologi-cal knowledge generation and flow between the agents involved in innovation processes, and the impact on the route of technological learning

La arquitectura popular indicador socioeconómico del medio rural. Situación en Cantabria.

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Coordinating heterogeneous IoT devices by means of the centralized vision of the SDN controller

The IoT (Internet of Things) has become a reality during recent years. The desire of having everything connected to the Internet results in clearly identified benefits that will impact on socio economic development. However, the exponential growth in the number of IoT devices and their heterogeneity open new challenges that must be carefully studied. Coordination among devices to adapt them to their users' context usually requires high volumes of data to be exchanged with the cloud. In order to reduce unnecessary communications and network overhead, this paper proposes a novel network architecture based on the Software-Defined Networking paradigm that allows IoT devices coordinate and adapt them within the scope of a particular context.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Analysis of the effect of clock drifts on frequency regulation and power sharing in inverter-based islanded microgrids

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Local hardware clocks in physically distributed computation devices hardly ever agree because clocks drift apart and the drift can be different for each device. This paper analyses the effect that local clock drifts have in the parallel operation of voltage source inverters (VSIs) in islanded microgrids (MG). The state-of-the-art control policies for frequency regulation and active power sharing in VSIs-based MGs are reviewed and selected prototype policies are then re-formulated in terms of clock drifts. Next, steady-state properties for these policies are analyzed. For each of the policies, analytical expressions are developed to provide an exact quantification of the impact that drifts have on frequency and active power equilibrium points. In addition, a closed-loop model that accommodates all the policies is derived, and the stability of the equilibrium points is characterized in terms of the clock drifts. Finally, the implementation of the analyzed policies in a laboratory MG provides experimental results that confirm the theoretical analysis.Peer ReviewedPostprint (author's final draft

Identification and Assessment of Livestock Best Management Practices (BMPs) Using the REED+ Approach in the Ecuadorian Amazon

Deforestation is a severe threat to diversity in the Ecuadorian Amazon Region (EAR). To mitigate deforestation, it is necessary to know the relevant stakeholders’ roles and interactions and deepen our knowledge of the local livelihoods, objectives, potentials, limitations, and “rights of being” among farms, as well as the best management practices (BMPs). In this study, our aim was to identify and assess livestock BMPs along an elevational gradient to foster sustainable production and reduce emissions from deforestation and forest degradation (REDD+). This approach could be environmentally and economically beneficial. Data were collected from 167 households along three elevational gradients, as well as from 15 interviews held among a multidisciplinary panel of key stakeholders and researchers in the EAR. The results showed that most of the Kichwa population lives in the medium zone, which features a larger agricultural and forest surface. Conversely, in the lower and upper areas, livestock predominates, where the upper area is specialized in milk production and the lower area in dual-purpose cattle (meat and dairy). The stakeholder assessment provided several key results: (a) social, structural, and technical factors have complementary effects on BMP adoption; (b) the sixteen assessed BMPs facilitated the implementation of existing financial incentive programs and enabled public–private partnerships to develop REDD+ projects. The policy implications of implementing these approaches are also discussed