Vincent Blondel

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The focused organization theory of social ties proposes that the structure of human social networks can be arranged around extra-network foci, which can include shared physical spaces such as homes, workplaces, restaurants, and so on. Until now, this has been difficult to investigate on a large scale, but the huge volume of data available from online(More)
We analyze two large datasets from technological networks with location and social data: user location records from an online location-based social networking service, and anonymized telecommunications data from a European cellphone operator, in order to investigate the differences between individual and group behavior with respect to physical location. We(More)
This report describes a 3-year-old boy who presented with skin lesions characterized by multiple streaks of hyperpigmentation following Blaschko's lines since 6 weeks of age. The clinical features are consistent with the diagnosis of linear and whorled nevoid hypermelanosis (LWNH), but differ substantially from this entity by the pigmentary incontinence(More)
We show that some basic linear control design problems are NP-hard, implying that, unless P=NP, they cannot be solved by polynomial time algorithms. The problems that we consider include simultaneous stabilization by output feedback, stabilization by state or output feedback in the presence of bounds on the elements of the gain matrix, and decentralized(More)
We show that the simultaneous stabilization question: When are three linear systems stabilizable by the same controller? cannot be solved by a semialgebraic set description nor be answered by computational machines. Contrary to the case of two systems, the underlying innnite-dimensional space of controllers cannot be bypassed. Simultaneous stabilization of(More)
This paper presents a novel meta algorithm, Partition-Merge (PM), which takes existing centralized algorithms for graph computation and makes them distributed and faster. In a nutshell, PM divides the graph into small subgraphs using our novel randomized partitioning scheme, runs the centralized algorithm on each partition separately, and then stitches the(More)
Our main result disproves conjectures on simultaneous stabilizability conditions by showing tha t , unlike the case of two plants, the existence of a simultaneous stabilizing controller for more than two plants is not guaranteed by the existence of a controller such that the closed loops have no real unstable poles. We include an example of a plant tha t is(More)