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A framework for cascade size calculations on random networks
(2017)arXivWe present a framework to calculate the cascade size evolution for a large class of cascade models on random network ensembles in the limit of infinite network size. Our method is exact and applies to network ensembles with almost arbitrary degree distribution, degreedegree correlations and, in case of threshold models, with arbitrary threshold distribution. With our approach, we shift the perspective from the known branching process ...Working Paper 
Generalized Hypergeometric Ensembles: Statistical Hypothesis Testing in Complex Networks
(2016)arXivStatistical ensembles define probability spaces of all networks consistent with given aggregate statistics and have become instrumental in the analysis of relational data on networked systems. Their numerical and analytical study provides the foundation for the inference of topological patterns, the definition of networkanalytic measures, as well as for model selection and statistical hypothesis testing. Contributing to the foundation ...Working Paper 
The network structure of cityfirm relations
(2015)arXivHow are economic activities linked to geographic locations? To answer this question, we use a datadriven approach that builds on the information about location, ownership and economic activities of the world's 3,000 largest firms and their almost one million subsidiaries. From this information we generate a bipartite network of cities linked to economic activities. Analysing the structure of this network, we find striking similarities ...Working Paper 
The spatial component of R&D networks
(2015)arXivWe study the role of geography in R&D networks by means of a quantitative, microgeographic approach. Using a large database that covers international R&D collaborations from 1984 to 2009, we localize each actor precisely in space through its latitude and longitude. This allows us to analyze the R&D network at all geographic scales simultaneously. Our empirical results show that despite the high importance of the city level, transnational ...Working Paper 
A model of dynamic rewiring and knowledge exchange in R&D networks
(2015)arXivThis paper investigates the process of knowledge exchange in interfirm Research and Development (R&D) alliances by means of an agentbased model. Extant research has pointed out that firms select alliance partners considering both networkrelated and networkunrelated features (e.g. social capital versus complementary knowledge stocks). In our agentbased model, firms are located in a metric knowledge space. The interaction rules incorporate ...Working Paper 
How Damage Diversification Can Reduce Systemic Risk
(2015)arXivWe consider the problem of risk diversification in complex networks. Nodes represent e.g. financial actors, whereas weighted links represent e.g. financial obligations (credits/debts). Each node has a risk to fail because of losses resulting from defaulting neighbors, which may lead to large failure cascades. Classical risk diversification strategies usually neglect network effects and therefore suggest that risk can be reduced if possible ...Working Paper 
The value of peripheral nodes in controlling multilayer networks
(2015)arXivWe analyze the controllability of a twolayer network, where driver nodes can be chosen only from one layer. Each layer contains a scalefree network with directed links. The dynamics of nodes depends on the incoming links from other nodes (reputation dynamics). We find that the controllable part of the network is larger when choosing peripherial nodes to connect the two layers. The control is as efficient for peripherial nodes as driver ...Working Paper 
An ensemble perspective on multilayer networks
(2015)arXivWe study properties of multilayered, interconnected networks from an ensemble perspective, i.e. we analyze ensembles of multilayer networks that share similar aggregate characteristics. Using a diffusive process that evolves on a multilayer network, we analyze how the speed of diffusion depends on the aggregate characteristics of both intra and interlayer connectivity. Through a blockmatrix model representing the distinct layers, ...Working Paper 
Selection rules in alliance formation
(2014)arXivWe study how firms select partners using a large database of publicly announced R&D alliances over a period of 25 years. We identify, for the first time, two distinct behavioral strategies of firms in forming these alliances. By reconstructing and analysing the temporal R&D network of 14,000 international firms and 21.000 publicly announced alliances, we find a "universal" behavior in firms changing between these strategies. In the first ...Working Paper 
Newcomers vs. incumbents: How firms select their partners for R&D collaborations
(2014)arXivThis paper studies the selection of partners for R&D collaborations of firms both empirically, by analyzing a large data set of R&D alliances over 25 years, and theoretically, by utilizing an agentbased model of alliance formation. We quantify the topological position of a firm in the R&D network by means of the weighted kcore decomposition which assigns a coreness value to each firm. The evolution of these coreness values over time ...Working Paper