Probabilistic memory-one strategies to dominate the iterated prisoner’s dilemma over networks

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe Iterated Prisoner’s Dilemma (IPD) has been a classical game theoretical scenario used to model behaviour interactions among agents. From the famous Axelrod’s tournament, and the successful results obtained by the Tit for Tat strategy, to the introduction of the zerodeterminant strategies in the last decade, the game theory community has been exploring the performance of multiple strategies for years. This article grounds on such previous work, studying probabilistic memory-one strategies (PMO) and using evolutionary game theory, to analyse the criteria to find the most successful set of strategies in networked topologies. The results are nearly deterministic in discrete PMO scenarios. However, results become much more complex when moving to continuous ones, and there is no optimal strategy for a given scenario. Finally, this article describes how, using machine learning and evolutionary techniques; a cluster of agents, playing synchronously and adaptively, is able to dominate the rest of the populatio

Synchronization in complex networks

Synchronization processes in populations of locally interacting elements are in the focus of intense research in physical, biological, chemical, technological and social systems. The many efforts devoted to understand synchronization phenomena in natural systems take now advantage of the recent theory of complex networks. In this review, we report the advances in the comprehension of synchronization phenomena when oscillating elements are constrained to interact in a complex network topology. We also overview the new emergent features coming out from the interplay between the structure and the function of the underlying pattern of connections. Extensive numerical work as well as analytical approaches to the problem are presented. Finally, we review several applications of synchronization in complex networks to different disciplines: biological systems and neuroscience, engineering and computer science, and economy and social sciences.Comment: Final version published in Physics Reports. More information available at http://synchronets.googlepages.com

Strategic and Selfless Interactions: a study of human behaviour

Los seres humanos son animales únicos, cooperando en una escala sin par en cualquier otra especie. Construimos sociedades compuestas de individuos no emparentados, y resultados empíricos nos han demostrado que las personas tienen preferencias sociales y pueden estar dispuestas a tomar acciones costosas que beneficien a otros. Por otro lado, los seres humanos también compiten entre ellos mismos, lo que en ocasiones conlleva consecuencias negativas como la sobreutilización de recursos naturales. Sin embargo, la competición entre agentes económicos subyace el funcionamiento adecuado de los mercados, y su destabilización -- tal como en una distribución desbalanceada de poder de mercado -- puede ser dañina a la eficiencia comercial. Por consiguiente, analizar cómo las personas cooperan y compiten es de importancia primordial para el entendimiento del comportamiento humano, especialmente al considerar los desafíos inminentes que amenazan el bienestar futuro de nuestras sociedades.En esta tesis, se presentan trabajos analizando el comportamiento de las personas en dilemas sociales -- situaciones en las cuales decisiones egoístas discrepan del optimo social -- y en otros escenarios estratégicos. Utilizando el framework de la teoría de juegos, sus interacciones tienen lugar en juegos abstrayendo estas situaciones. Específicamente, realizamos experimentos conductuales en los cuales las personas participaron en juegos adaptados de recursos comunes, de bienes públicos y otros juegos hechos a medida. Además, con la intención de comprender la existencia de la cooperación en humanos, proponemos un enfoque teórico para modelar su evolución a través de una dinámica de selección de heurísticas.Empezamos presentando los fundamentos teóricos y empíricos en los que se basa esta tesis, a saber, la teoría de juegos, la economía experimental, la ciencia de redes y la evolución de la cooperación. Posteriormente, ilustramos los aspectos prácticos de la realización de experimentos mediante implementaciones de software.Para comprender el comportamiento de las personas en problemas de acción colectiva -- como la mitigación del cambio climático, que requiere un nivel global de coordinación y cooperación -- realizamos juegos de bienes públicos y recursos comunes entre participantes chinos y españoles. Los resultados obtenidos proporcionan algunas ideas sobre las variaciones y universalidades de las respuestas de las personas en estos escenarios.En esta línea, durante los últimos años, las personas e instituciones están cada vez más preocupadas por los temas sociales y ambientales. Sin embargo, las contribuciones en estos escenarios requieren un nivel sustancial de altruismo por parte de los agentes que tienen que tomar decisiones costosas. Realizamos dos experimentos para comprender los factores que impulsan dichas decisiones en dos situaciones de relevancia contemporánea: las donaciones benéficas y las inversiones socialmente responsables. Sus resultados indican que el encuadre y otras características sociodemográficas están asociadas significativamente con decisiones prosociales y altruistas.Además, también hemos analizado el comportamiento de las personas en un escenario competitivo y complejo en el cual los sujetos participaron como intermediarios en experimentos de formación de precios. Lo hacemos a través de un experimento que implementa en redes complejas una generalización del juego de negociación. Nuestros hallazgos indican efectos significativos de la topología de la red tanto en resultados experimentales como también en modelos teóricos basados en el comportamiento observado.Por último, exponemos un trabajo teórico que intenta comprender el surgimiento de la cooperación a través de un enfoque novedoso para estudiar la evolución de estrategias en poblaciones estructuradas. Esto se logra modelando las decisiones de los agentes como resultados de heurísticas, siendo estas heurísticas seleccionadas mediante un proceso inspirado en los algoritmos evolutivos. Nuestros análisis muestran que, cuando estos agentes tienen memoria de sus interacciones anteriores, las estrategias cooperativas prosperarán. Sin embargo, esas estrategias funcionarán de acuerdo con diferentes heurísticas según la información que tomen en consideración.<br /

Self-Organising Networks in Complex Infrastructure Projects: The Case of London Bank Station Capacity Upgrade Project

Managing large infrastructure projects remains a thorny issue in theory and practice. This is mainly due to their increasingly interconnected, interdependent, multilateral, nonlinear, unpredictable, uncontrollable, and rapidly changing nature. This study is an attempt to demystify the key issues to the management of large construction projects, arguing that these projects are delivered through networks that evolve in ways that we do not sufficiently understand as yet. The theoretical framework of this study is grounded in Complexity Theory; a theory resulted in a paradigm shift when it was first introduced to project management post-2000 but is yet to be unpacked in its full potential. The original contribution of the study is predicated on perceiving large construction projects as evolving complex systems that involves a high degree of self‐organisation. This is a process that transitions contractually static prescribed roles to dynamic network roles, comprising individuals exchanging information. Furthermore, by placing great emphasis upon informal communications, this study demonstrates how self-organising networks can be married with Complexity Theory. This approach has the potential to make bedfellows around the concept of managing networks within a context of managing projects; a concept that is not always recognised, especially in project management. With the help of social network analysis, two snapshots from Bank Station Capacity Upgrade Project Network were analysed as a case study. Findings suggest that relationships and hence network structures in large construction projects exhibit small-world topology, underlined by a high degree of sparseness and clustering. These are distinct structural properties of self-organising networks. Evidence challenges the theorisation about self-organisation which largely assumes positive outcomes and suggests that self-organising could open up opportunities yet also create constraints. This helps to provide further insights into complexity and the treatment of uncertainty in large projects. The study concludes with detailed recommendations for research and practice

An Initial Framework Assessing the Safety of Complex Systems

Trabajo presentado en la Conference on Complex Systems, celebrada online del 7 al 11 de diciembre de 2020.Atmospheric blocking events, that is large-scale nearly stationary atmospheric pressure patterns, are often associated with extreme weather in the mid-latitudes, such as heat waves and cold spells which have significant consequences on ecosystems, human health and economy. The high impact of blocking events has motivated numerous studies. However, there is not yet a comprehensive theory explaining their onset, maintenance and decay and their numerical prediction remains a challenge. In recent years, a number of studies have successfully employed complex network descriptions of fluid transport to characterize dynamical patterns in geophysical flows. The aim of the current work is to investigate the potential of so called Lagrangian flow networks for the detection and perhaps forecasting of atmospheric blocking events. The network is constructed by associating nodes to regions of the atmosphere and establishing links based on the flux of material between these nodes during a given time interval. One can then use effective tools and metrics developed in the context of graph theory to explore the atmospheric flow properties. In particular, Ser-Giacomi et al. [1] showed how optimal paths in a Lagrangian flow network highlight distinctive circulation patterns associated with atmospheric blocking events. We extend these results by studying the behavior of selected network measures (such as degree, entropy and harmonic closeness centrality)at the onset of and during blocking situations, demonstrating their ability to trace the spatio-temporal characteristics of these events.This research was conducted as part of the CAFE (Climate Advanced Forecasting of sub-seasonal Extremes) Innovative Training Network which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 813844

Understanding cluster dynamics in evolutionary economic geography : essays on the structure of networks and clusters life style

L’objectif principal de cette thèse est d’étudier l’évolution des clusters. La littérature concernant les clusters s’est longuement intéressée aux raisons de leur existence ainsi qu’à la manière dont ils favorisent l’innovation, la productivité et la croissance. Nous étudions comment ces effets durent dans le temps, poursuivant l’objectif d’identifier les déterminants de la performance dynamique des clusters. Il s’agit, ainsi, d’expliquer pourquoi certains clusters déclinent tandis que d’autres continuent à fonctionner grâce à un renouveau constant. Cette thèse adopte une approche des clusters par les réseaux. Nous défendons l’idée que les structures de réseau hétérogènes des clusters démontrent des capacités différentes à s’associer ou à se dissocier des cycles industriels/technologiques au bon moment. Ainsi, nous identifions les propriétés de structure du réseau qui favorisent la performance dynamique des clusters ou la résilience des clusters. Nous appuyons nos développements théoriques sur des regards empiriques dans deux contextes bien différents. D’une part, nous étudions les structures des clusters de l’industrie de la téléphonie mobile en Europe. D’autre part, nous analysons la structure des relations entre les producteurs de fromage d’Aculco (Mexique). Le résultat principal de ce travail montre que la hiérarchie et la disassortativité des réseaux, ainsi que les interactions entre des réseaux de natures différentes (multiplexité), influencent la capacité des clusters à éviter les lock-in négatifs, conduisant à leur déclin, et favorisent le lock-out pour la survie du cluster, c’est-à-dire la prolongation de leur vie.The main objective of this thesis is to study clusters’ evolution. The literature on clusters has widely studied why clusters exist and how they favor innovation, productivity and growth. Our concern is to study how these effects hold over time. Therefore, we aim at identifying the determinants of dynamic performance of clusters to explain why some clusters decline while others keep working by continuous renewal. To do so, this thesis approaches clusters from a network perspective. We contend that clusters with heterogeneous network structures exhibit different capacities to associate and dissociate cluster’s evolution and industrial/technological cycle at the right moment. Thus, we identify the properties of network structures that favor dynamic performance of clusters or cluster resilience. We support our theoretical developments with empirical insights in two different contexts. On the one hand, we study the structure of clusters in the European mobile phone industry. On the other hand, we analyze the structure of relations between cheese producers in Aculco (Mexico). The main result of this work is that network hierarchy, network disassortativity and the interplay between different networks (multiplexity) influence the capacity of clusters to avoid negative lock-in leading to cluster failure, and favor lock-out to enhance cluster continuation, i.e. extending the life of the cluster

Global urbanization and food production in direct competition for land:Leverage places to mitigate impacts on SDG2 and on the Earth System

Global urbanization and food production are in direct competition for land. This paper carries out a critical review of how displacing crop production from urban and peri-urban land to other areas – because of issues related to soil quality – will demand a substantially larger proportion of the Earth’s terrestrial land surface than the surface area lost to urban encroachment. Such relationships may trigger further distancing effects and unfair social-ecological teleconnections. It risks also setting in motion amplifying effects within the Earth System. In combination, such multiple stressors set the scene for food riots in cities of the Global South. Our review identifies viable leverage points on which to act in order to navigate urban expansion away from fertile croplands. We first elaborate on the political complexities in declaring urban and peri-urban lands with fertile soils as one global commons. We find that the combination of an advisory global policy aligned with regional policies enabling robust common properties rights for bottom-up actors and movements in urban and peri-urban agriculture (UPA) as multi-level leverage places to intervene. To substantiate the ability of aligning global advisory policy with regional planning, we review both past and contemporary examples where empowering local social-ecological UPA practices and circular economies have had a stimulating effect on urban resilience and helped preserve, restore, and maintain urban lands with healthy soils