Detecting communities in complex networks accurately is a prime challenge, preceding further analyses of network characteristics and dynamics. Until now, community detection took into account only positively valued links, while many actual networks also feature negative links. We extend an existing Potts model to incorporate negative links as well,… (More)
(PP olos, 1991). We wish to thank the AJS reviewers for their insightful comments and Jeroen Bruggeman, Michael Masuch, and GG abor P eli for comments on earlier drafts. All theorems in the article are proved by the automated theorem prover Otter (Organized Techniques for Abstract This article presents a formal reconstruction of James D. Thompson's classic… (More)
Qualitative reasoning is traditionally associated with the domain of physics, although the domain of application is, in fact, much broader. This paper investigates the application of qualitative reasoning beyond the domain of physics. It presents a case study of application in the social sciences: the density dependence theory of organizational ecology. It… (More)
Network diversity yields context-dependent benefits that are not yet fully-understood. I elaborate on a recently introduced  distinction between tie strength diversity and information source diversity, and explain when, how, and why they matter. The issue whether there are benefits to specialization is the key.
Resource partitioning theory claims that " Increasing concentration enhances the life chances of specialist organizations. " We systematically think through this theory, specify implicit background assumptions, sharpen concepts, and rigorously check the theory's logic. As a result, we increase the theory's explanatory power, and claim— contrary to received… (More)
Diffuse competition due to niche overlap between actors without (direct) ties with each other, constrains their structural autonomy. This is not dealt with in Burt's mathematical model of his well-known structural holes theory. We fix his model by introducing a network measure of niche overlap. In structural holes, the social structure of competition, Burt… (More)
Distribution of competition in organizational markets. Learning organizations in action-a system dynamics model of satisficing search with adaptive aspirations Computer simulation has had a long and established tradition in the social sciences. Unfortunately, research in this field has always been at the margin. Why? After all, computer simulations allow us… (More)
Collective violence in direct confrontations between two opposing groups happens in short bursts wherein small subgroups briefly attack small numbers of opponents , while the majority of participants forms a supportive audience. These bursts and subgroups' small sizes are explained by Kuramoto's synchronization model, which also clarifies leaders' role.