Complex systems in areas such as biology, physics, social science, and technology are extensively modeled as networks due to the rich set of tools available for their study and analysis. In such networks, groups of nodes that correspond to functional units or those that share some common attributes result in densely connected structures called communities. Community formation is an inherent process, and it is not easy to detect these structures because of the complex ways in which components of these systems interact.

Detecting communities in complex networks is important because it helps us to understand their internal dynamics better, thereby leading to significant insights into the underlying systems. Overlapping communities are formed when nodes in the network simultaneously belong to more than one community, and it has been shown that most real networks naturally contain such an overlapping community structure. In this thesis, I introduce a new approach to overlapping community detection called IDLE that incorporates ideas from another interesting problem: the identification of influential spreaders. Influential spreaders are nodes that play an important role in the propagation of information or diseases in networks. Research suggests that the main core identified by k-core decomposition techniques are the most influential spreaders. In my approach, I use these k-cores as candidate seeds for local community detection. Following a well-defined seed selection process, IDLE builds and prunes their corresponding local communities. It then augments the resulting local communities and puts them together to obtain the global overlapping community structure of the network.

My approach improves on the current local community detection techniques, because they use either random nodes or maximal k-cliques as seeds, and they do not focus explicitly on detecting overlapping nodes in the network. Hence their results can be significantly improved in building ground-truth overlapping communities. The results of my experiments on real and synthetic networks indicate that IDLE results in enhanced overlapping community detection and thereby a better identification of overlapping nodes that could be important or influential components in the underlying system.