1,720,998 research outputs found
Terrestrial Transportation Networks and Power Balance in Etruria and Latium Vetus between the beginning of the Early Iron Age and the end of the Archaic Period
No full textIn base alla Network analysis si analizza l'evoluzione dei modelli insediamentali tra prima età del ferro ed età arcaica tra Latium Vetus ed Etruri
Synchronization of moving integrate and fire oscillators
Full text linkWe present a model of integrate and fire oscillators that move on a plane. The phase of the oscillators evolves linearly in time and when it reaches a threshold value they fire choosing their neighbors according to a certain interaction range. Depending on the velocity of the ballistic motion and the average number of neighbors each oscillator fires to, we identify different regimes shown in a phase diagram. We characterize these regimes by means of novel parameters as the accumulated number of contacted neighbors.Fil: Prignano, Luce. Universidad de Barcelona. Facultad de Física. Departamento de Física Fomental; EspañaFil: Sagarra, Oleguer. Universidad de Barcelona. Facultad de Física. Departamento de Física Fomental; EspañaFil: Gleiser, Pablo Martin. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Díaz Guilera, Albert. Universidad de Barcelona. Facultad de Física. Departamento de Física Fomental; Españ
Consensus formation in the Deffuant model of opinion dynamics
Full text linkTreballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2023, Tutor: Luce PrignanoThis final project aims at exploring the emergence of consensus states in the already classic Deffuant model of opinion dynamics. In order to do so, four definitions are proposed and serve as the ground of the subsequent treatment. The results start off with a brief study of the general behavior of the model, as well as of the influence that both initial conditions and the convergence parameter μ exert upon it. After this, a comparison of the original model with two proposed variations of it is carried out, providing further insight into the mechanisms behind the phenomena of interest. Finally, a probabilistic study based on a simplified model of these mechanisms is introduced
Ancient regional transportation infrastructures as co-evolving complex systems: a multiplex network approach
Full text linkTreballs Finals de Màster en Física dels Sistemes Complexos i Biofísica, Facultat de Física, Universitat de Barcelona. Curs: 2021-2022. Tutora: Luce PrignanoNetwork theory has demonstrated to be an invaluable tool for studying complex systems, and it has been widely used in many disciplines. Archaeology is no exception. Ancient transportation infrastructures (TIs) are often represented as networks of interacting settlements. However, these various TIs are different in nature, and the network they form requires a different approach. Here we show that ancient TIs as a whole can be characterized by a multiplex. After an analysis of the dynamic performance and structural properties of the individual road and river networks of Southern Etruria and Latium Vetus in the Iron Age (950 − 580 BC), we overlap both TIs by regarding them as layers in a multiplex. We then study the multiplex with the aim to assess how good the interplay between layers is. Our work thus serves as a case study of an empirical multiplex network. We prove that the tools we use are good to characterize ancient TIs as one multiplex and could become very powerful if further studied and refined
Mapping opinion landscapes: analyzing network structures in climate change debates on Twitter
No full textTreballs Finals de Màster en Física dels Sistemes Complexos i Biofísica, Facultat de Física, Universitat de Barcelona. Curs: 2022-2023. Tutors: Luce Prignano, Emanuele CozzoSociety is a complex system, and studying it is challenging. We need to develop mechanisms to obtain data for statistical analysis. Our goal is to collect a substantial amount of data on a subject while also understanding how human opinion is structured and how it evolves over time, providing us with additional insights. With the advent of online social platforms, we have the opportunity to study how users generate content (data) and how others interact with this content.
This presents us with a perfect tool and opens up an entire universe of possibilities.
In this project, we aim to characterize opinions on the issue of climate change using Twitter data [1]. The focus of this research lies in developing a method to study the structure of human opinions. To achieve this, we will analyze three Twitter discussions where users are expected to take positions on climate change-related policies, express their opinion about COP Meetings, and discuss the creation of the 2030 Agenda among Catalan and Spanish speakers. By capturing these data based on user opinions, we will conduct a study by analyzing the networks that shape these opinions and interactions. Through this analysis, we hope to uncover the underlying structure of a Twitter discussion within the framework of complex networks. Additionally, we will attempt to identify if distinct communities are formed and who the most influential accounts are in each case.
We aim to assess the polarization of the network to determine if there are two clear sides [2]. On one hand, we anticipate users who support or oppose the climate change issue, and on the other hand, we aim to identify a ”denialist” side that opposes the concept of climate change. Expanding our study, we can also track the evolution of public opinion. Nevertheless, we must acknowledge certain limitations. Not everyone uses Twitter, resulting in incomplete representation of all communities.
Furthermore, such platforms do not necessarily mirror real-world interactions, yet they do offer a robust reflection of public opinion beyond the screens.
The results have been less encouraging in terms of polarization. For most of the cases studied, we observed a dominant structure that does not exhibit clear polarization for or against the idea of climate change. However, we did identify another noteworthy type of structure worth discussing.
In conclusion, the hypothesis that the ”denialist” side possesses significant enough support to disrupt other types of structures has not proven accurate. Nonetheless, we discovered that these debates are often steered by highly influential hubs. Analyzing these hubs can provide us with a solid understanding of the current opinion landscape
Mapping opinion landscapes: analyzing network structures in climate change debates on Twitter
Full text linkTreballs Finals de Màster en Física dels Sistemes Complexos i Biofísica, Facultat de Física, Universitat de Barcelona. Curs: 2022-2023. Tutors: Luce Prignano, Emanuele CozzoSociety is a complex system, and studying it is challenging. We need to develop mechanisms to obtain data for statistical analysis. Our goal is to collect a substantial amount of data on a subject while also understanding how human opinion is structured and how it evolves over time, providing us with additional insights. With the advent of online social platforms, we have the opportunity to study how users generate content (data) and how others interact with this content.
This presents us with a perfect tool and opens up an entire universe of possibilities.
In this project, we aim to characterize opinions on the issue of climate change using Twitter data [1]. The focus of this research lies in developing a method to study the structure of human opinions. To achieve this, we will analyze three Twitter discussions where users are expected to take positions on climate change-related policies, express their opinion about COP Meetings, and discuss the creation of the 2030 Agenda among Catalan and Spanish speakers. By capturing these data based on user opinions, we will conduct a study by analyzing the networks that shape these opinions and interactions. Through this analysis, we hope to uncover the underlying structure of a Twitter discussion within the framework of complex networks. Additionally, we will attempt to identify if distinct communities are formed and who the most influential accounts are in each case.
We aim to assess the polarization of the network to determine if there are two clear sides [2]. On one hand, we anticipate users who support or oppose the climate change issue, and on the other hand, we aim to identify a ”denialist” side that opposes the concept of climate change. Expanding our study, we can also track the evolution of public opinion. Nevertheless, we must acknowledge certain limitations. Not everyone uses Twitter, resulting in incomplete representation of all communities.
Furthermore, such platforms do not necessarily mirror real-world interactions, yet they do offer a robust reflection of public opinion beyond the screens.
The results have been less encouraging in terms of polarization. For most of the cases studied, we observed a dominant structure that does not exhibit clear polarization for or against the idea of climate change. However, we did identify another noteworthy type of structure worth discussing.
In conclusion, the hypothesis that the ”denialist” side possesses significant enough support to disrupt other types of structures has not proven accurate. Nonetheless, we discovered that these debates are often steered by highly influential hubs. Analyzing these hubs can provide us with a solid understanding of the current opinion landscape
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Reconstruction, mobility, and synchronization in complex networks
Full text link[eng] During the last decades, it has become clear that systems formed by many interacting parts show emergent dynamical properties which are inherently related to the topology of the underlying pattern of connections among the constituent parts.
Such systems, usually known as complex systems, are in general suitably described through their networks of contacts, that is, in terms of nodes (representing the system's components) and edges (standing for their interactions), which allows to catch their essential features in a simple and general representation.
In recent years, increasing interest on this approach, thanks also to a favorable technological progress, led to the accumulation of an increasing amount of data. This situation has allowed the arising of new questions and, therefore, the diversification of the scientific work.
Among them, we can point out three general issues that have been receiving a lot of interest: (i) is the available information always reliable and complete? (ii) how does a complex interaction pattern affect the emergence of collective behavior in complex systems? And (iii) which is the role of mobility within the framework of complex networks?
This thesis has been developed along these three lines, which are strictly interrelated. We expand on three case-studies, each one of which deals with two the above mentioned macro-issues.
We consider the issue of the incompleteness of the available information both in the case of natural (Chapter 2) and artificial (Chapter 3) networks.
As a paradigmatic emergent behavior, we focus on the synchronization of coupled phase oscillators (Chapter 2 and Chapter 4), deeply investigating how different patterns of connections can affect the achievement of a globally coherent state.
Finally, we include moving agents in two different frameworks, using them as explorers of unknown networks (Chapter 3) and considering them as interacting units able to establish connections with their neighbors (Chapter 4).
In Chapter 2, we study the problem of the reconstruction of an unknown interaction network, whose nodes are Kuramoto oscillators.
Our aim is to extract topological features of the connectivity pattern from purely dynamical measures, based on the fact that in a heterogeneous network the global dynamics is not only affected by the distribution of the natural frequencies but also by the location of the different values.
The gathered topological information ranges from local features, such as the single node connectivity, to the hierarchical structure of functional clusters, and even to the entire adjacency matrix.
In Chapter 4, instead, we present a model of integrate and fire oscillators that are moving agents, freely displacing on a plane. The phase of the oscillators evolves linearly in time and when it reaches a threshold value they fire at their neighbors.
In this way, the interaction network is a dynamical object by itself since it is re-created at each time step by the motion of the units. Depending on the velocity of the motion, the average number of neighbors, the coupling strength and the size of the agents population, we identify different regimes.
Moving agents are employed also in Chapter 3 where they play the role of explorers of unknown artificial networks, having the mission to recover information about their structures.
We propose a model in which random walkers with previously assigned home nodes navigate through the network during a fixed amount of time. We consider that the exploration is successful if the walker gets the information gathered back home, otherwise, no data is retrieved. We show that there is an optimal solution to this problem in terms of the average information retrieved and the degree of the home nodes and design an adaptive strategy based on the behavior of the random walker.[spa] Durante las últimas décadas, se ha empezado a poner de manifiesto que sistemas formados por muchos elementos en interacción pueden mostrar propiedades dinámicas emergentes relacionadas con la topología del patrón de conexiones entre las partes constituyentes.
Estos sistemas, generalmente conocidos como sistemas complejos, en muchos casos pueden ser descritos a través de sus redes de contactos, es decir, en términos de nodos (que representan los componentes del sistema) y de enlaces (sus interacciones). De esta manera es posible capturar sus características esenciales en una representación simple y general.
En esta última década, el creciente interés en este enfoque, gracias también a un progreso tecnológico favorable, ha llevado a la acumulación de una cantidad ingente de datos.
Eso, a su vez, ha permitido el surgimiento de nuevas preguntas y, por lo tanto, la diversificación de la actividad científica.
Entre ellas, podemos destacar tres cuestiones generales que son objeto de mucho interés: (i) ¿la información disponible es siempre fiable y completa? (ii) ¿cómo un patrón de interacción complejo puede afectar el surgimiento de comportamientos colectivos? Y (iii) ¿cual es el papel de la movilidad en el marco de las redes complejas?
Esta tesis se ha desarrollado siguiendo estas tres líneas, que están íntimamente relacionadas entre sí. Hemos profundizado en tres casos de estudio, cada uno de los cuales se ocupa de dos de los macro-temas mencionados.
Consideramos la cuestión del carácter incompleto de la información disponible tanto en el caso de redes naturales (Capítulo 2) como de redes artificiales (Capítulo 3).
Nos centramos en la sincronización de los osciladores de fase acoplados (Capítulos 2 y 4) en cuanto comportamiento emergente paradigmático, investigando en profundidad cómo los diferentes patrones de conexión puedan afectar la consecución de un estado coherente a nivel global.
Por último, analizamos el rol de la movilidad incluyendo agentes móviles en dos marcos diferentes. En un caso, los utilizamos como exploradores de redes desconocidas (Capítulo 3), mientras que en otro los consideramos como unidades que interaccionan y son capaces de establecer conexiones con sus vecinos (Capítulo 4)
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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