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arXiv2011

Mathematical formalism of physics of systems with motivation

The paper discusses fundamental problems in mathematical description of social systems based on physical concepts, with so-called statistical social systems being the main subject of consideration. Basic properties of human beings and human societies that distinguish social and natural systems from each other are listed to make it clear that individual mathematical formalism and physical notions should be developed to describe such objects rather then can be directly inherited from classical mechanics and statistical physics. As a particular example systems with motivation are considered. Their characteristic features are analyzed individually and the appropriate mathematical description is proposed. Finally the paper concludes that the basic elements necessary for describing statistical social systems or, more rigorously, systems with motivation are available or partly developed in modern physics and applied mathematics.

physics.soc-ph↗

arXiv2009

The International-Trade Network: Gravity Equations and Topological Properties

This paper begins to explore the determinants of the topological properties of the international - trade network (ITN). We fit bilateral-trade flows using a standard gravity equation to build a "residual" ITN where trade-link weights are depurated from geographical distance, size, border effects, trade agreements, and so on. We then compare the topological properties of the original and residual ITNs. We find that the residual ITN displays, unlike the original one, marked signatures of a complex system, and is characterized by a very different topological architecture. Whereas the original ITN is geographically clustered and organized around a few large-sized hubs, the residual ITN displays many small-sized but trade-oriented countries that, independently of their geographical position, either play the role of local hubs or attract large and rich countries in relatively complex trade-interaction patterns.

q-fin.GN↗

arXiv2009

Other-regarding preferences and altruistic punishment: A Darwinian perspective

This article examines the effect of different other-regarding preference types on the emergence of altruistic punishment behavior from an evolutionary perspective. Our findings corroborate, complement, and interlink the experimental and theoretical literature that has shown the importance of other-regarding behavior in various decision settings. We find that a selfish variant of inequity aversion is sufficient to quantitatively explain the level of punishment observed in contemporary experiments: If disadvantageous inequity aversion is the predominant preference type, altruistic punishment emerges in our model to a level that precisely matches the empirical observations. We use a new approach that closely combines empirical results from a public goods experiment together with an evolutionary simulation model. Hereby we apply ideas from behavioral economics, complex system science, and evolutionary biology.

physics.soc-ph↗

arXiv2009

Indifferents as an interface between Contra and Pro

In most sociophysical simulations on public opinion, only two opinions are allowed: Pro and Contra. However, in all political elections many people do not vote. Here we analyse two models of dynamics of public opinion, taking into account Indifferent voters: {\it i)} the Sznajd model with symmetry Pro-Contra, {\it ii)} the outflow one move voter model, where Contra's are converted to Indifferent by their Pro neighbours. Our results on the Sznajd model are in an overall agreement with the results of the mean field approach and with those known from the initial model formulation. The simulation on the voter model shows that an amount of Contra's who remain after convertion depends on the network topology.

physics.soc-ph↗

arXiv2009

Comparing university organizational units and scientific co-authorship communities

A co-authorship network of scientists at a university is an archetypical example of a complex evolving network. Collaborative R&D networks are self-organized products of partner choice between scientists. Modern science is, due to the immanent imperative of newness, strongly interdisciplinary. Crossovers between the different scientific disciplines and organizational units are observable on a daily basis. Since collaborative research has become the dominant and most promising way to produce high-quality output, collaboration structures are also a target for research and management design. We study co-authorship covered by the Citation Index within University College Dublin, a large Irish university. We focus especially on collaborations between organizational units, such as schools or colleges. We compare the centrality of the brokerage individuals within their organizational units. The network of co-authorship is analyzed with standard network measures, with typical features for complex networks observed. We use the bipartite network of authors and papers for the identification of communities of collaborators and clusters of papers. The observed communities are compared to the formal organizational units of the university.

physics.soc-ph↗

arXiv2009

Smallworld bifurcations in an opinion model

We study a cellular automaton opinion formation model of Ising type, with antiferromagnetic pair interactions modeling anticonformism, and ferromagnetic plaquette terms modeling the social norm constraints. For a sufficiently large connectivity, the mean-field equation for the average magnetization (opinion density) is chaotic. This "chaoticity" would imply irregular coherent oscillations of the whole society, that may eventually lead to a sudden jump into an absorbing state, if present. However, simulations on regular one-dimensional lattices show a different scenario: local patches may oscillate following the mean-field description, but these oscillations are not correlated spatially, so the average magnetization fluctuates around zero (average opinion near one half). The system is chaotic, but in a microscopic sense where local fluctuations tend to compensate each other. By varying the long-range rewiring of links, we trigger a small-world effect. We observe a bifurcation diagram for the magnetization, with period doubling cascades ending in a chaotic phase. As far as we know, this is the first observation of a small-world induced bifurcation diagram. The social implications of this transition are also interesting. In the presence of strong "anticonformistic" (or "antinorm") behavior, efforts for promoting social homogenization may trigger violent oscillations.

physics.soc-ph↗

arXiv2009

Independence and interdependence in the nest-site choice by honeybee swarms: agent-based models, analytical approaches and pattern formation

In a recent paper List, Elsholtz and Seeley [Phil. Trans. Roy. Soc. B. 364 (2009) 755] have devised an agent-based model of the the nest-choice dynamics in swarms of honeybees, and have concluded that both interdependence and independence are needed for the bees to reach a consensus on the best nest site. We here present a simplified version of the model which can be treated analytically with the tools of statistical physics and which largely has the same features as the original dynamics. Based on our analytical approaches it is possible to characterize the co-ordination outcome exactly on the deterministic level, and to a good approximation if stochastic effects are taken into account, reducing the need for computer simulations on the agent-based level. In the second part of the paper we present a spatial extension, and show that transient non-trivial patterns emerge, before consensus is reached. Approaches in terms of Langevin equations for continuous field variables are discussed.

q-bio.PE↗

arXiv2009

Taylor's power law for fluctuation scaling in traffic

In this article, we study transportation network in Minnesota. We show that the system is characterized by Taylor's power law for fluctuation scaling with nontrivial values of the scaling exponent. We also show that the characteristic exponent does not unequivocally characterize a given road network, as it may differ within the same network if one takes into account location of observation points, season, period of day, or traffic intensity. The results are set against Taylor's fluctuation scaling in the Nagel-Schreckenberg cellular automaton model for traffic. It is shown that Taylor's law may serve, beside the fundamental diagram, as an indicator of different traffic phases (free flow, traffic jam etc.).

physics.soc-ph↗

arXiv2009

An individual-based model of collective attention

In our modern society, people are daily confronted with an increasing amount of information of any kind. As a consequence, the attention capacities and processing abilities of individuals often saturate. People, therefore, have to select which elements of their environment they are focusing on, and which are ignored. Moreover, recent work shows that individuals are naturally attracted by what other people are interested in. This imitative behaviour gives rise to various herding phenomena, such as the spread of ideas or the outbreak of commercial trends, turning the understanding of collective attention an important issue of our society. In this article, we propose an individual-based model of collective attention. In a situation where a group of people is facing a steady flow of novel information, the model naturally reproduces the log-normal distribution of the attention each news item receives, in agreement with empirical observations. Furthermore, the model predicts that the popularity of a news item strongly depends on the number of concurrent news appearing at approximately the same moment. We confirmed this prediction by means of empirical data extracted from the website digg.com. This result can be interpreted from the point of view of competition between the news for the limited attention capacity of individuals. The proposed model, therefore, provides new elements to better understand the dynamics of collective attention in an information-rich world.

physics.soc-ph↗

arXiv2010

The Shield that Never Was: Societies with Single-Peaked Preferences are More Open to Manipulation and Control

Much work has been devoted, during the past twenty years, to using complexity to protect elections from manipulation and control. Many results have been obtained showing NP-hardness shields, and recently there has been much focus on whether such worst-case hardness protections can be bypassed by frequently correct heuristics or by approximations. This paper takes a very different approach: We argue that when electorates follow the canonical political science model of societal preferences the complexity shield never existed in the first place. In particular, we show that for electorates having single-peaked preferences, many existing NP-hardness results on manipulation and control evaporate.

cs.GT↗

arXiv2009

Structure Profile by a Model of Precipitation

The organizational structure of a network is investigated with a simulated precipitation model which does not make use of prior knowledge about the community structure of the network. The result is presented as a structure profile through which various definitions of communities can be applied for specific applications. The simulated precipitation model performs the grouping of nodes so that nodes belonging to the same 'community' automatically aggregate, thereby revealing regions of the adjacency matrix with denser interconnections. The process is analogous to massive particles precipitating towards the lower potential layer. Without loss of the infrastructure information, a community structure profile of a network can be obtained as the ground state of the Hamiltonian. The method is also applicable to directed and weighted networks.

cond-mat.mtrl-sci↗

arXiv2009

Some collaboration-competition bipartite networks

Recently, we introduced a quantity, "node weight", to describe the collaboration sharing or competition gain of the elements in the collaboration-competition networks, which can be well described by bipartite graphs. We find that the node weight distributions of all the networks follow the so-called "shifted power law (SPL)". The common distribution function may indicate that the evolution of the collaboration and competition in very different systems obeys a general rule. In order to set up a base of the further investigations on the universal system evolution dynamics, we now present the definition of the networks and their node weights, the node weight distributions, as well as the evolution durations of 15 real world collaboration-competition systems which are belonging to diverse fields.

physics.soc-ph↗

arXiv2009

Models of the World human population growth- critical analysis

We analyze mathematical models of the global human population growth and compare them to actual dynamics of the world population and of the world surplus product. We consider a possibility that the so-called world's demographic transition is not a dynamic crossover but a phase transition that affects all aspects of our life.

physics.soc-ph↗

arXiv2009

Scaling property and opinion model for interevent time of terrorism attack

The interevent time of terrorism attack events is investigated by empirical data and model analysis. Empirical evidence shows it follows a scale-free property. In order to understand the dynamic mechanism of such statistic feature, an opinion dynamic model with memory effect is proposed on a two-dimension lattice network. The model mainly highlights the role of individual social conformity and self-affirmation psychology. An attack event occurs when the order parameter of the system reaches a critical value. Ultimately, the model reproduces the same statistical property as the empirical data and gives a good understanding of terrorism attack.

physics.soc-ph↗

arXiv2014

Une étude de physique sur les élections

We study spatiotemporal regularities of electoral results and turnout rates for each municipality (or polling station) concerning French elections between 1992 and 2007. We try to account for the data using models based on a simple imitation of agents in the vicinity. We also propose a model of an experiment that shows how choices are modified by knowing the choices of others agents.

physics.soc-ph↗

arXiv2010

Terrorism: Mechanisms of Radicalization Processes, Control of Contagion and Counter-Terrorist Measures

The spread of radical ideologies is a key to fanaticism, recruitment and terrorist activities. Hence, preventing such activities requires predictive models capable of identifying areas and agents before occurrence of catastrophic terrorist act. In this paper, we develop a model that captures a radicalization mechanism through several intermediate stages of individuals. We propose a radicalizatiom mechanism using individual-based approach constructed from epidemiological model of contagion. Our model builds on insights from contagion models used in theoretical epidemiology and entails a mechanism for controlling the spread of radical ideologies on social spatial networks by identifying suspicious individuals and monitoring them, and taking action when necessary. We show how our model can combat the development of terrorist networks even with limited information on a target terrorist network.

physics.soc-ph↗

arXiv2010

Price Trends in a Simplified Model of the Wealth Game

We consider a simplified version of the Wealth Game, which is an agent-based financial market model with many interesting features resembling the real stock market. Market makers are not present in the game so that the majority traders are forced to reduce the amount of stocks they trade, in order to have a balance in the supply and demand. The strategy space is also simplified so that the market is only left with strategies resembling the decisions of optimistic or pessimistic fundamentalists and trend-followers in the real stock market. A dynamical phase transition between a trendsetters' phase and a bouncing phase is discovered in the space of price sensitivity and market impact. Analysis based on a semi-empirical approach explains the phase transition and locates the phase boundary. A phase transition is also observed when the fraction of trend-following strategies increases, which can be explained macroscopically by matching the supply and demand of stocks.

physics.soc-ph↗

arXiv2010

Investigating an online social network using spatial interaction models

Using a spatial interaction modeling approach, we investigate the German collegiate social network site StudiVZ. We focus on identifying factors that foster strong inter-institutional linkages, testing whether the acquaintanceship rate between institutions of higher education is related to various geographic and institutional attributes. We find that acquaintanceship is most significantly related to geographic separation: measuring distance with automobile travel time, acquaintanceship drops by 91% for each additional 100 minutes. Institution type and the former East-West German divide are also related to this rate with statistical significance.

physics.soc-ph↗