| Sunday | Monday | Tuesday | Wednesday | Thursday | Friday |
This page lists the abstracts for the talks part of the ECCS08 conference
| Monday Talks Abstracts | ||
|---|---|---|
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Itzhak Aharon Hebrew University |
The relationship between rationality and the mechanisms of human decision-making: Inputs from Neuroeconomis abstract |
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Luís M. A. Bettencourt Los Alamos National Laboratory |
The rules of information aggregation and the advantages of collective information processing Information is a peculiar quantity. Unlike matter or energy, the aggregation of knowledge from many sources can in fact produce more (or less) information than the sum of its parts. I use the formalism of information theory to derive general principles of information aggregation and collective organization under which information pooling can be synergetic or to identify when it will be redundant. I then show how several problems of collective distributed information processing can be understood in terms of the conditions that allow for the minimization of uncertainty (maximization of predictability) under information pooling over many units. We apply these principles to the reverse engineering of living neuronal networks from data and to collective spatial searches for stochastic signals. In this way we reveal specific network structures and rigorously assert their functional information processing roles. Finally, I discuss how collective information processing principles may provide a unified perspective into observation of the dynamics of swarms, markets, and statistical patterns in natural languages, among other complex systems, and identify empirical, technological and conceptual challenges that lie ahead towards establishing a theory of collective cognition. |
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Stefano Boccaletti Istituto Nazionale di Ottica Applicata |
Scale-free topologies emerging from a dynamical entrainment of a complex network I show that the topology and dynamics of a network of unsynchronized Kuramoto oscillators can be simultaneously controlled by means of a forcing mechanism which yields a phase locking of the oscillators to that of an external pacemaker in connection with the reshaping of the network's degree distribution. The entrainment mechanism is based on the addition, at regular time intervals, of unidirectional links from oscillators that follow the dynamics of a pacemaker to oscillators in the pristine graph whose phases hold a prescribed phase relationship. Such a dynamically based rule in the attachment process leads to the emergence of a power-law shape in the final degree distribution of the graph whenever the network is entrained to the dynamics of the pacemaker. I show that the arousal of a scale-free distribution in connection with the success of the entrainment process is a robust feature, characterizing different network's initial configurations and parameters. |
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Damien Challet ISI Foundation |
The therapy to shock therapy: optimal dynamical policies for transition economies. We show that a simple model reproduces very closely the evolution of the gross domestic product (GDP) in current and constant dollars of many countries during the times of recession and recovery. A theoretical analysis illustrates how an optimal dynamical policy reduces both recession duration and severity, and increases the value of GDP at all times. We propose a criterion to distinguish a posteriori a dynamical policy from a static one. Finally, we predict that Ukraine will recover its current and constant dollar 1990 GDPs in 2009 and Moldova in 2015 in current dollars and 2009 in constant dollars. |
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Bernard Derrida Ecole Normale Supérieure |
Genealogies in models of evolution with selection Simples mean field models of evolution in presence of selection will be discussed. The effect of selection is to modify the statistical properties of genealogical trees: while in absence of selection, the trees are randomly distributed as in Kingman's coalescent, their statistics, in presence of selection, are very reminisecent of Parisi's theory of mean field spin glasses. |
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Giovanni Dosi Sant'Anna School of Advanced Studies |
Micro heterogeneity and macroeconomic regularities features of economic self-organization abstract |
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Sol Efroni NIH |
Title abstract |
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Santo Fortunato ISI Foundation |
Towards a physics of society Statistical physics has proven to be an invaluable tool to describe and understand the properties of systems formed by a large number of elementary units. A big challenge is whether the tools and techniques of statistical physics are suitable to explore large scale social phenomena. Most attempts of the literature focus on simple microscopic models, with little or no contact to real social dynamics. A validation of this approach is still lacking and must rely on quantitative evidence about real social systems. Finding regularities on real data is a crucial step in this direction. We will show that voting and citing behaviors are both characterized by scaling and universality. The statistical distribution of the number of votes/cites, suitably normalized, is independent of the particular system considered. This opens the way to a simple modeling of the observed phenomenology. |
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Moshe Idel Hebrew University |
Complexities: Synchronic and Diachronic abstract |
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Yoram Louzoun Bar-Ilan University |
Direct Measurement of Information Network's Evolution abstract |
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Matteo Marsili ICTP |
Volatility and the emergence of social networks The very notion of networks in socio-economic systems relies on the fact that both the agents composing it and their relationships are stable to some degree. In reality both change in time as a result of a large variety of (often unobservable) factors -- which we call volatility. For a given type of socio-economic interaction among agents, dense networks can exist only if volatility is not strong enough. We show, in simple stylized models of evolving networks, that the transition to a dense network is sharp and discontinuous when volatility affects mainly the links, whereas it turns continuous when volatility affects mostly nodes (high agents' turnover). [1] http://arxiv.org/abs/0807.0348 |
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Elchanan Mossel UC Berkeley |
title abstract |
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Luciano Pietronero University of Rome "La Sapienza" |
Minimal agent based model for the origin and self-organization of financial markets We introduce a minimal Agent Based Model which includes the following elements (first considered by Lux and Marchesi): - Fundamentalists (F: stabilizing tendency) - Chartists (C: destabilizing tendency) - Herding effect (tendency to follow the others) - Price behavior (analysis of the price time series according to F or C criteria) The novelty of our model is a substantial simplification and corresponding reduction of the number of parameters. This leads to a detailed understanding of the origin of the Stylized Facts (SF) like the fat tails and volatility clustering. The SF are shown to correspond to finite size effects (with respect to time and to the number of agents N) which, however, can be active at different time scales. This implies that universality cannot be expected in describing these properties in terms of effective critical exponents. A basic question is then the self-organization: why the system chooses to stay in this narrow range of parameters corresponding also to a finite value of N? We show that the introduction of a threshold in the agents’ action (small price fluctuations lead to no action) triggers the self-organization towards the quasi-critical state and to a finite average value of N (which depends on the other parameters). Non stationarity in the number of active agents and in their action plays a fundamental role. The interpretation of N as the number of effective independent agents is non trivial and deserves further studies. The model can be easily generalized to more realistic variants in a systematic way. |
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Harold Scheraga Cornell University |
Evolution of experimental and theoretical approaches to determine protein structure and protein folding pathways Our efforts in protein simulation originated from our early theoretical considerations of the effect of hydrogen bonds on protein reactivity , and of the physical origin of hydrophobic interactions and their effect on protein reactivity. Applications of these ideas to experimental studies of bovine pancreatic ribonuclease A led to the identification of three tyrosyl…aspartate interactions which serve as distance constraints on the folding of the backbone chain, and thus, with the aid of an empirical potential function, help to simulate the three-dimensional structure. This motivated our initial development of an all-atom force field and methods for its global optimization to compute protein structure. Initial results from applications of this approach led to structures of the cyclic decapeptide gramicidin S, models of the fibrous protein collagen, and the three-helix bundle of the 46-residue protein A , all of which were verified by experiment. These developments, and the need to extend the all-atom model to a physics-based united-residue (UNRES) one, to be able to apply simulation methods to proteins larger than protein A, will be discussed, together with results with UNRES in CASP blind tests. |
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Nadav Shnerb Bar-Ilan University |
From companies to colonies: Pareto-like distributions in ecosystems. Recent studies of cluster distribution in various ecosystems revealed Pareto statistics for the size of spatial colonies. These results were supported by cellular automata simulations that yield robust criticality for endogenous pattern formation based on positive feedback. We show that this self-organized criticality is a manifestation of the law of proportion effect, first discovered in the context of business firm size. Mapping the stochastic model to a Markov birth-death process, the transition rates are shown to scale linearly with cluster size. This mapping provides a connection between patch statistics and the dynamics of the ecosystem; the "first passage time" for different colonies emerges as a powerful tool that discriminates between endogenous and exogenous clustering mechanisms. The effects of other ecological parameters, like resource local competition and threshold size, are considered and the possible predictability of imminent catastrophic shifts (like desertification) is discussed. |
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Ricard V. Solé Universitat Pompeu Fabra |
title abstract |
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Eugene Stanley Boston University |
Applications of Statistical Physics to Understanding Complex Systems abstract |
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Dietrich Stauffer University of Cologne |
Demography - Who pays my pension ? Simple computer simulations indicate in many European countries serious problems for old-age pensions around 2030 or later: Many more old people and much less young people. Possible remedies are immigration and increase in retirement ages. In Algeria the present situation seems better balanced, in the Palestinian Territories it is the opposite, for the next few decades. |
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Duncan Watts Yahoo! Research |
Social science 2.0? Social science is often concerned with the emergence of collective behavior out of the interactions of large numbers of individuals; but in this regard it has long suffered from a severe measurement problem—namely that interactions between people are hard to measure, especially at scale, over time, and at the same time as observing behavior. In this talk, I will argue that the technological revolution of the Internet is beginning to lift this constraint. To illustrate, I will describe three examples of research that would have been extremely difficult, or even impossible, to perform just a decade ago: (1) using email exchange to track social networks evolving in time; (2) using a web-based experiment to study the collective consequences of social influence on decision making; and (3) using a social networking site to study the difference between perceived and actual homogeneity of attitudes among friends. Although internet-based research still faces serious methodological and procedural obstacles, I propose that the ability to study truly “social” dynamics at individual-level resolution will have dramatic consequences for social science. |