Coevolution of agents and networks: Opinion spreading and community disconnection

We study a stochastic model for the coevolution of a process of opinion formation in a population of agents and the network which underlies their interaction. Interaction links can break when agents fail to reach an opinion agreement. The structure of the network and the distribution of opinions over the population evolve towards a state where the population is divided into disconnected communities whose agents share the same opinion. The statistical properties of this final state vary considerably as the model parameters are changed. Community sizes and their internal connectivity are the quantities used to characterize such variations.Comment: To appear in Phys. Lett.

Adapting Quality Assurance to Adaptive Systems: The Scenario Coevolution Paradigm

From formal and practical analysis, we identify new challenges that self-adaptive systems pose to the process of quality assurance. When tackling these, the effort spent on various tasks in the process of software engineering is naturally re-distributed. We claim that all steps related to testing need to become self-adaptive to match the capabilities of the self-adaptive system-under-test. Otherwise, the adaptive system's behavior might elude traditional variants of quality assurance. We thus propose the paradigm of scenario coevolution, which describes a pool of test cases and other constraints on system behavior that evolves in parallel to the (in part autonomous) development of behavior in the system-under-test. Scenario coevolution offers a simple structure for the organization of adaptive testing that allows for both human-controlled and autonomous intervention, supporting software engineering for adaptive systems on a procedural as well as technical level.Comment: 17 pages, published at ISOLA 201

Actor-relational planning in deprived areas : challenges and opportunities in luchtbal Antwerpen, Belgium

In this article we report and discuss our experience with actor relational approaches in the regeneration of a post war housing estate in Luchtbal, Antwerp, Belgium. Actor relational approaches are informed by post-structuralist ideas of space, complexity theory and actor network theory. Although ARA itself is not new, the application of ARA to deprived area’s such as Luchtbal is novel. We report how the approach has been elaborated, its process and outcome. We conclude with our evaluation from an insider’s perspective

Coevolutionary Competence in the Realm of Corporate Longevity: How Long-lived Firms Strategically Renew Themselves

Understanding the phenomena of corporate longevity and self-renewing organizations has become an important topic in recent management literature. However, the majority of the research contributions focus on internal determinants of longevity and self-renewal. Using a co-evolutionary framework, the purpose of this paper is to address the dynamic interaction between organizations and environments in the realm of sustained strategic renewal, i.e. corporate longevity. To this end, we will focus on the competence of long-lived firms to coevolve due to the joint effect of managerial intentionality and environmental selection pressures. Building on coevolutionary framework, we develop a conceptual framework that highlights an organization’s coevolutionary competence. Two longitudinal case studies are presented illustrating the arguments.strategic renewal;corporate longevity;competence-based management;adaptive open systems;coevolutionary competence

Anticipation and the Non-linear Dynamics of Meaning-Processing in Social Systems

Social order does not exist as a stable phenomenon, but can be considered as "an order of reproduced expectations." When anticipations operate upon one another, they can generate a non-linear dynamics which processes meaning. Although specific meanings can be stabilized, for example in social institutions, all meaning arises from a global horizon of possible meanings. Using Luhmann's (1984) social systems theory and Rosen's (1985) theory of anticipatory systems, I submit algorithms for modeling the non-linear dynamics of meaning in social systems. First, a self-referential system can use a model of itself for the anticipation. Under the condition of functional differentiation, the social system can be expected to entertain a set of models; each model can also contain a model of the other models. Two anticipatory mechanisms are then possible: a transversal one between the models, and a longitudinal one providing the system with a variety of meanings. A system containing two anticipatory mechanisms can become hyper-incursive. Without making decisions, however, a hyper-incursive system would be overloaded with uncertainty. Under this pressure, informed decisions tend to replace the "natural preferences" of agents and a knowledge-based order can increasingly be shaped

Complex dynamics in coevolution models with ratio-dependent functional response

We explore the complex dynamical behavior of two simple predator-prey models of biological coevolution that on the ecological level account for interspecific and intraspecific competition, as well as adaptive foraging behavior. The underlying individual-based population dynamics are based on a ratio-dependent functional response [W.M. Getz, J. Theor. Biol. 108, 623 (1984)]. Analytical results for fixed-point population sizes in some simple communities are derived and discussed. In long kinetic Monte Carlo simulations we find quite robust, approximate 1/f noise in species diversity and population sizes, as well as power-law distributions for the lifetimes of individual species and the durations of periods of relative evolutionary stasis. Adaptive foraging enhances coexistence of species and produces a metastable low-diversity phase and a stable high-diversity phase.Comment: 19 page

Three phases in the evolution of the standard genetic code: how translation could get started

A primordial genetic code is proposed, having only four codons assigned, GGC meaning glycine, GAC meaning aspartate/glutamate, GCC meaning alanine-like and GUC meaning valine-like. Pathways of ambiguity reduction enlarged the codon repertoire with CUC meaning leucine, AUC meaning isoleucine, ACC meaning threonine-like and GAG meaning glutamate. Introduction of UNN anticodons, in a next episode of code evolution in which nonsense elimination was the leading theme, introduced a family box structure superposed on the original mirror structure. Finally, growth rate was the leading theme during the remaining repertoire expansion, explaining the ordered phylogenetic pattern of aminoacyl-tRNA synthetases. The special role of natural aptamers in the process is high-lighted, and the error robustness characteristics of the code are shown to have evolved by way of a stepwise, restricted enlargement of the tRNA repertoire, instead of by an exhaustive selection process testing myriads of codes

Coupled dynamics of node and link states in complex networks: A model for language competition

Inspired by language competition processes, we present a model of coupled evolution of node and link states. In particular, we focus on the interplay between the use of a language and the preference or attitude of the speakers towards it, which we model, respectively, as a property of the interactions between speakers (a link state) and as a property of the speakers themselves (a node state). Furthermore, we restrict our attention to the case of two socially equivalent languages and to socially inspired network topologies based on a mechanism of triadic closure. As opposed to most of the previous literature, where language extinction is an inevitable outcome of the dynamics, we find a broad range of possible asymptotic configurations, which we classify as: frozen extinction states, frozen coexistence states, and dynamically trapped coexistence states. Moreover, metastable coexistence states with very long survival times and displaying a non-trivial dynamics are found to be abundant. Interestingly, a system size scaling analysis shows, on the one hand, that the probability of language extinction vanishes exponentially for increasing system sizes and, on the other hand, that the time scale of survival of the non-trivial dynamical metastable states increases linearly with the size of the system. Thus, non-trivial dynamical coexistence is the only possible outcome for large enough systems. Finally, we show how this coexistence is characterized by one of the languages becoming clearly predominant while the other one becomes increasingly confined to "ghetto-like" structures: small groups of bilingual speakers arranged in triangles, with a strong preference for the minority language, and using it for their intra-group interactions while they switch to the predominant language for communications with the rest of the population.Comment: 21 pages, 15 figure