Adaptive Dynamics of Realistic Small-World Networks

Continuing in the steps of Jon Kleinberg's and others celebrated work on decentralized search in small-world networks, we conduct an experimental analysis of a dynamic algorithm that produces small-world networks. We find that the algorithm adapts robustly to a wide variety of situations in realistic geographic networks with synthetic test data and with real world data, even when vertices are uneven and non-homogeneously distributed. We investigate the same algorithm in the case where some vertices are more popular destinations for searches than others, for example obeying power-laws. We find that the algorithm adapts and adjusts the networks according to the distributions, leading to improved performance. The ability of the dynamic process to adapt and create small worlds in such diverse settings suggests a possible mechanism by which such networks appear in nature

Network Information Flow in Small World Networks

Recent results from statistical physics show that large classes of complex networks, both man-made and of natural origin, are characterized by high clustering properties yet strikingly short path lengths between pairs of nodes. This class of networks are said to have a small-world topology. In the context of communication networks, navigable small-world topologies, i.e. those which admit efficient distributed routing algorithms, are deemed particularly effective, for example in resource discovery tasks and peer-to-peer applications. Breaking with the traditional approach to small-world topologies that privileges graph parameters pertaining to connectivity, and intrigued by the fundamental limits of communication in networks that exploit this type of topology, we investigate the capacity of these networks from the perspective of network information flow. Our contribution includes upper and lower bounds for the capacity of standard and navigable small-world models, and the somewhat surprising result that, with high probability, random rewiring does not alter the capacity of a small-world network.Comment: 23 pages, 8 fitures, submitted to the IEEE Transactions on Information Theory, November 200

Collective navigation of complex networks: Participatory greedy routing

Many networks are used to transfer information or goods, in other words, they are navigated. The larger the network, the more difficult it is to navigate efficiently. Indeed, information routing in the Internet faces serious scalability problems due to its rapid growth, recently accelerated by the rise of the Internet of Things. Large networks like the Internet can be navigated efficiently if nodes, or agents, actively forward information based on hidden maps underlying these systems. However, in reality most agents will deny to forward messages, which has a cost, and navigation is impossible. Can we design appropriate incentives that lead to participation and global navigability? Here, we present an evolutionary game where agents share the value generated by successful delivery of information or goods. We show that global navigability can emerge, but its complete breakdown is possible as well. Furthermore, we show that the system tends to self-organize into local clusters of agents who participate in the navigation. This organizational principle can be exploited to favor the emergence of global navigability in the system.Comment: Supplementary Information and Videos: https://koljakleineberg.wordpress.com/2016/11/14/collective-navigation-of-complex-networks-participatory-greedy-routing

Neighbor selection and hitting probability in small-world graphs

Small-world graphs, which combine randomized and structured elements, are seen as prevalent in nature. Jon Kleinberg showed that in some graphs of this type it is possible to route, or navigate, between vertices in few steps even with very little knowledge of the graph itself. In an attempt to understand how such graphs arise we introduce a different criterion for graphs to be navigable in this sense, relating the neighbor selection of a vertex to the hitting probability of routed walks. In several models starting from both discrete and continuous settings, this can be shown to lead to graphs with the desired properties. It also leads directly to an evolutionary model for the creation of similar graphs by the stepwise rewiring of the edges, and we conjecture, supported by simulations, that these too are navigable.Comment: Published in at http://dx.doi.org/10.1214/07-AAP499 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Education and Training Needs in the Field of Logistic Structures and Services in the Lower Danube Region

The approach of the subject concerning the training of specialists in the domain of logistic structures and services in the region of the inferior Danube is enlisted within a larger context, the Strategy of the Danube, but also in a more restrained one, the Program of Cross-Border Cooperation Romania – Bulgaria, 2007-2013. The Strategy of the Danube represents a project initiated in the year 2008 by Germany, Austria and Romania to which subsequently there adhered the other states on the Danube and which became a program of the European Commission. It shall have allotted a budget of 50 milliards euro until the year 2013. It shall be preponderantly addressed to the population in the Danube Basin, which is estimated at 115 millions, following to be developed through cross-border projects. In December 2010 there is foreseen the approval of the Action Plan for the program the Strategy of the Danube by the European Commission. The integration process needs premises and conditions for further development. One of them is the connectivity and it supporting system – the logistics. The problem of the connectivity is one of the pillars of the Danube strategy, which could play an important role in the Lower Danube Macro region’s development. Those problems need different approaches, specialized research and training. The situation of the two countries in the domain of fluvial logistics may be characterized as unsatisfactory in relation to their potential. At the present moment there is a single bridge which connects the two countries (Giurgiu – Ruse) and several travels with the passage boat. The harbour infrastructures are old and inefficient. There are no modern multi-modal platforms or a coherent vision in their design. The transportation on the Danube is insufficiently exploited. As well, the river is not capitalized in other domains, too: agriculture, pisciculture, energy, ecology, tourism, arrangement of the territory, etc.Within a more restrained context, but correlated with the Strategy of the Danube, Romania and Bulgaria cooperate within the Cross-Border Program 2007-2013. Within it, the Academy of Economic Studies in Bucharest and thee Economic Academy Dimitar Apostolov Tsenov in Svishtov proposed themselves to collaborate in the domain “Cooperation concerning the development of human resources – the joint development of abilities and knowledge”.fluvial logistics, multi-modal platform, education, transportation, cross-border, Lower Danube Macro region, territorial connectivity