Research

Network theory, structure and models

Network theory has recently become a key ingredient in the description, analysis and understanding of a large variety of complex systems which can be characterized in terms of networks. Real-world examples range from networks of social contacts to networks of biological interactions, ecological systems, information architectures, infrastructures and many others. The main activity of our research in this area is the analysis and characterization of the network's structure and the development of models aimed at the understanding of the global behavior of these systems. Purely topological properties are studied together with potential additional features of the network, such as weights to represent the strength or the kind of interaction, nodes' features or internal structures, directionality, etc.

Publications

Information Networks

The Internet was originally conceived as an infrastructure aimed at helping the research effort, and surprisingly enough its success has led to a large-scale system that has become a scientific challenge by itself. This network is the outcome of a self organization process that gives rise to a large-scale infrastructure whose study is the object of an intense research activity. The same happened with the many application networks (WWW, P2P etc.) living on its physical structure. We are interested in both the characterization and modeling of these networks in connection with the social systems driving their growth and function.

Publications

Epidemic modeling

We are interested in the study of epidemic models in complex networks and systems. We approach this area from two directions. The first one is the theoretical perspective aimed at studying the basic theory that govern epidemic behavior in large-scale complex multi-scale network and agent-based epidemic models. The second one is the study of realistic models that progressively incorporate different social databases and infrastructures networks. This implies the construction of an open source computational platform that integrates epidemic models with a large variety of social and transportation data.

Publications

Social systems

This part of our research activity is devoted to the study of social networks and of models for social phenomena on networks. Social interactions are indeed commonly described by statistical physics models and studied by statistical physics tools: for example, in models of opinion formation, agents update their internal state, or opinion, through an interaction with their neighbors. Here we study how the complex topology of these interactions, which form complex self-organized networks, affects the dynamics of social phenomena such as the propagation of a rumor, or the emergence of a consensus between interacting agents. Other topics of research concern the study of the topology and evolution of social networks (such as collaboration networks), the detection of community structures, or the understanding of the mechanisms of search engines on the WWW.

Publications

Infrastructures

Electrical power grids, airline connections, gas and oil transportation grids, water distribution networks, road and railway transportation systems are all examples of infrastructures which play fundamental roles in our everyday lives. Their characterization in terms of networked systems allows for the analysis of their structure to get an insight on their evolution, stability and global behavior. Topics like vulnerability to attacks, identification of strategies to reduce and mitigate risks, introduction of new methods and tools for the study of the system architecture, optimization of the infrastructure to enhance the performance of the system, role of spatial geography in the evolution and functioning of the network represent some of the problems we are currently investigating.

Publications

Biological networks

The recent availability of high-throughput gene expression and proteomics techniques has created an unprecedented opportunity for a comprehensive study of the structure and dynamics of many biological systems. In particular, these systems can be synthetically represented as complex networks which exhibit peculiar features far from the random paradigm. Our research activity in this context focuses on the characterization and modeling of biological networks, in particular protein-protein interaction networks. The analysis of their structure can uncover peculiar organizational mechanisms - such as correlation signatures, rich-club hierarchies, modularity - which provide further insights into the biological significance of these complex systems.
People involved: V. Colizza, A. Flammini, A. Vespignani

Publications