Events
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Speaker
Joan T. MatamalasDescription
Dynamical processes running on complex networks have been largely studied due to their suitability to model very different scenarios. Understanding critical aspects of ecological systems, modeling how traffic flows in a city or modeling relations between species in ecosystem are a few examples of their potential applications. Nevertheless, there are some inherent limitations imposed by the way how these traditionally models are built, that could diminish their analytical power. For instance, consider the case of modeling mobility on a city. There, users can move between different places using different transportation systems, bus, subway, taxi, etc. Embedding this multimodality of systems inside our mobility model is critical to understand how it will behave in situations like congestion or failures since, different transportation modes have different capacities, costs or speeds. However, traditional network representations cannot embed this heterogeneity since the relations that they represent have to share a common definition. To overcome this issue, we should increase the structural complexity order of our model, enabling the use of different kinds of relations.
On this thesis, we focus on the understanding of how increasing the order of dynamical models, i.e., the amount of information represented, concerning structure, relational correlations, and temporal information, and their effects on three topics that profoundly affect our lives: the emergence of cooperation, the spreading of epidemics and, finally, human mobility. We show that this increase on the complexity has a significant contribution to the way how we understand the way these processes work.
- 2018
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Speaker
Rosalba García-Millán( Imperial College, London, UK)Description
Braching processes have been widely studied and applied to model phenomena such as gambling, percolation and avalanching. In my talk, I will present our field-theoretic approach to continuous-time branching processes, a method that allows us to calculate new observables such as the temporal scaling of the moments of the instant population size, the so-called avalanche shape, the n-point correlation function and the probability density function of the total avalanche size. This is joint work with Johannes Pausch, Benjamin Walter and Gunnar Pruessner (preprint arXiv:1808.08418).
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Speaker
Guillermo GarcíaDescription
Thesis defense. Advisors: Prof. M. Ángeles Serrano and Dr. Marián Boguñá.
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Speaker
Dominik Lips and Philipp Maass (Department of Physics, Osnabrück University, Germany)Description
Models of driven stochastic particle transport in one dimension have been applied to describe such diverse phenomena as biopolymerization, molecular motor motion along filaments, flow of molecules through nanopores, ion conduction through membrane channels, electron transport along molecular wires, and vehicular traffic. A simple lattice model, the asymmetric simple exclusion process (ASEP) appears as a basic building block in the theoretical description of these driven diffusion systems and has developed into one of the standard models for investigating non-equilibrium steady states. After an introduction to the physics of the ASEP and some model variants with the focus on non-equilibrium phase transitions [1-3], we address the question whether corresponding phenomena will occur in driven Brownian motion, making them more amenable to experimental studies.
Specifically, we introduce a model of a Brownian asymmetric simple exclusion process (BASEP) with overdamped Brownian dynamics and a setup resembling that of the ASEP on a lattice [4]. In this BASEP, particles of size σ with hardcore interaction are driven by a constant drag force through a cosine potential with period λ and an amplitude much larger than the thermal energy.
We show that the character of the non-equilibrium steady states in the BASEP is strikingly different from that in the ASEP. Compared with a system of non-interacting particles, the current is enhanced for small σ/λ ratios due to a barrier reduction effect arising from multi-occupation of potential wells. Larger σ/λ ratios lead to a suppression of the current because of blocking effects. Surprisingly, an exchange- symmetry effect causes the current-density relation to be identical to that of non- interacting particles for commensurable lengths σ=nλ, n=1,2... A behavior similar as for the ASEP is obtained only in a limited parameter regime. The rich behavior of the current-density relation leads to phase diagrams of non-equilibrium steady states with up to five different phases. The structure of these phase diagrams changes with varying σ/λ ratio.
[1] M. Dierl, P. Maass, and M. Einax, Phys. Rev. Lett. 108, 060603 (2012).
[2] M. Dierl, M. Einax, and P. Maass, Phys. Rev. E 87, 062126 (2013).
[3] M. Dierl, W. Dieterich, M. Einax, and P. Maass, Phys. Rev. Lett. 112, 150601 (2014).
[4] D. Lips, A. Ryabov, and P. Maass, Phys. Rev. Lett. 121, 160601 (2018).
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Description
La xarxa d'Internet, les xarxes d'amistat a les escoles, els insectes socials i els organismes són exemples de sistemes complexos que es basen no només en les propietats intrínseques dels components (reduccionisme), sinó també en les interaccions entre els seus components. Entendre l'origen de la complexitat és un aspecte fonamental per tractar els desafiaments del món actual. Un dels aspectes clau d'aquests sistemes es troba en la dificultat que hi ha amb la modelització i simulació computacional i que necessita un enfocament purament multidisciplinari i integrador de moltes disciplines del coneixement. En aquest curs farem una introducció als sistemes complexos i les eines bàsiques per tal d’analitzar-los, emfatitzant en la descripció necessàriament interdisciplinar.
Objectius
El principal objectiu és fer arribar als docents de secundària de diferents matèries el tipus de sistemes que s’estudien dins el marc del que avui en dia anomenem ciència dels sistemes complexos. Aquesta ciència, que no es pot associar de manera immediata a cap de les ciències que podríem anomenar dins la classificació “tradicional”, és per definició interdisciplinària, ja que integra successives escales de definició que pertanyen a les disciplines tradicionals. Una ciència que ens permet passar de la descripció de la cel·la als òrgans, als organismes i a les poblacions. De les interaccions entre neurones al cervell i d’aquí a la psicologia i a les xarxes socials. També de com d’importants són les matemàtiques per una correcte descripció d’aquest món i les noves eines computacionals.
Programa
8.45 – 9.00h
Acollida
9.00 – 9.15h
Presentació de complexitat.CAT.
Álvaro Corral Cano, president
9.15 – 10.00h
Introducció als sistemes complexos.
Albert Diaz Guilera, catedràtic de Física de la Matèria Condensada de la UB i director de l’Institute of Complex Systems (UBICS)
10.00 – 11.00h
Principis: Emergència i autoorganització.
Sergi Valverde, professor lector a la UPF i membre del Complex Systems Lab
11.00 – 11.30h
Cafè i Networking.
11.30 – 12.30h
Patrons de la complexitat: Fractals.
Sergi Valverde
12.30 – 13.30h
Fonaments educatius de les xarxes complexes.
Gemma Rosell, investigadora predoctoral al Complexity Lab Barcelona (ClabB) i membre del UBICS
13.30 – 14.00h
Ronda de preguntes als ponents i cloenda.
Destinataris: Personal docent de secundària interessat en la interdisciplinarietat
Se certificaran: 5 hores.
Places: 50
Preu: 10€
Període inscripció: del 30 de juliol al 2 de novembre de 2018.
Inscripció per Internet: Formulari de matrícula
Informació i consultes
A/e: icecursos@ub.edu
Tel.: 934 021 024Organizers
complexitat.cat (http://complexitat.cat)