%0 Journal Article %T Layer aggregation and reducibility of multilayer interconnected networks %A M. De Domenico %A V. Nicosia %A A. Arenas %A V. Latora %J Computer Science %D 2014 %I arXiv %R 10.1038/ncomms7864 %X Many complex systems can be represented as networks composed by distinct layers, interacting and depending on each others. For example, in biology, a good description of the full protein-protein interactome requires, for some organisms, up to seven distinct network layers, with thousands of protein-protein interactions each. A fundamental open question is then how much information is really necessary to accurately represent the structure of a multilayer complex system, and if and when some of the layers can indeed be aggregated. Here we introduce a method, based on information theory, to reduce the number of layers in multilayer networks, while minimizing information loss. We validate our approach on a set of synthetic benchmarks, and prove its applicability to an extended data set of protein-genetic interactions, showing cases where a strong reduction is possible and cases where it is not. Using this method we can describe complex systems with an optimal trade--off between accuracy and complexity. %U http://arxiv.org/abs/1405.0425v1