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The past few years have seen intensive research efforts carried out in some apparently unrelated areas of dynamic systems – delay-tolerant networks, opportunistic-mobility networks, social networks – obtaining closely related insights. Indeed, the concepts discovered in these investigations can be viewed as parts of the same conceptual universe; and the(More)
In this paper we study the problem of gathering in the same location of the plane a collection of identical oblivious mobile robots. Previous investigations have focused mostly on the unlimited visibility setting, where each robot can always see all the other ones, regardless of their distance. In the more difficult and realistic setting where the robots(More)
Consider a team of mobile software agents deployed to capture a (possibly hostile) intruder in a network. All agents, including the intruder move along the network links; the intruder could be arbitrarily fast, and aware of the positions of all the agents. The problem is to design the agents' strategy for capturing the intruder. The main efficiency(More)
Consider a set of n > 2 simple autonomous mobile robots (decentralized, asyn-chronous, no common coordinate system, no identities, no central coordination, no direct communication, no memory of the past, deterministic) moving freely in the plane and able to sense the positions of the other robots. We study the primitive task of gathering them at a point not(More)
Protecting agents from host attacks is a pressing security concern in networked environments supporting mobile agents. In this paper, we consider a <i>black hole:</i> a highly harmful host that disposes of visiting agents upon their arrival, leaving no observable trace of such a destruction. The task to identify the location of the harmful host is clearly(More)
In this paper we address the problem of mobile agents searching for a highly harmful item (called a black hole) in a ring network. The black hole is a stationary process that destroys visiting agents upon their arrival without leaving any observable trace of such a destruction. The task is to have at least one surviving agent able to unambiguously report(More)
In this paper we aim at an understanding of the fundamental algorithmic limitations on what a set of autonomous mobile robots can or cannot achieve. We study a hard task for a set of weak robots. The task is for the robots in the plane to form any arbitrary pattern that is given in advance. The robots are weak in several aspects. They are anonymous; they(More)
In this paper we present deterministic parallel algorithms for the coarse-grained multicomputer (CGM) and bulk synchronous parallel (BSP) models for solving the following well-known graph problems: (1) list ranking, (2) Euler tour construction in a tree, (3) computing the connected components and spanning forest, (4) lowest common ancestor preprocessing,(More)
Most instruments-formalisms, concepts, and metrics-for social networks analysis fail to capture their dynamics. Typical systems exhibit different scales of dynamics, ranging from the fine-grain dynamics of interactions (which recently led researchers to consider temporal versions of distance, connectivity, and related indicators), to the evolution of(More)