Project description
Higher-order networks and their emergent collective behaviours
Many real-world systems, from the brain to social networks and economies, involve group interactions among many elements. Understanding how collective behaviours emerge across scales is a fundamental open challenge. Renormalisation – redefinition of parameters to remove ‘aberrant’ phenomena derived from theory but not observed experimentally – has been successfully applied to pairwise structural interactions. It remains largely unexplored for higher-order structures and their dynamics. With the support of the Marie Skłodowska-Curie Actions programme, the HORNET project aims to fill this gap by developing a rigorous renormalisation framework for higher-order networks. With it, HORNET aims to investigate how collective behaviours change across scales, validating findings on real-world datasets including brain connectomes, social interactions and economic systems.
Objective
Complex systems exhibit collective behaviours that arise from group interactions, represented by networks beyond pairwise interactions, also known as higher-order networks. Since emergent phenomena often appear across scales, renormalization methods have recently been introduced for simple networks. However, only limited efforts have been made to extend renormalization to higher-order structures, leaving a substantial gap. This project addresses it by developing a principled renormalization framework for higher-order networks.
The approach introduces two complementary methods, both based on a hidden variables formulation. The first, Multiscale Higher-Order Network Renormalization, defines ensembles of random hidden-variable hypergraphs invariant under coarse graining. The second, Geometric Higher-Order Network Renormalization, embeds hypergraphs in metric spaces and performs renormalization by geometric proximity, where the geometric coordinates are themselves hidden variables.
In addition, the project will go beyond the common practice of applying renormalization exclusively to structure, by investigating its impact on higher-order dynamics. This includes processes governed by group mechanisms, such as higher-order spreading that captures diffusion over social channels, synchronization driven by group couplings, and Ising inspired models with Hamiltonians including higher-order interaction terms. Studying how these processes transform under coarse graining will reveal how collective behaviours change across scales, which dynamical features are preserved, and when macroscopic order emerges or vanishes.
Finally, the two frameworks will be tested on empirical datasets, including brain connectomes, temporal social interactions and economic systems. This comparative validation will assess the distinctive multiscale signatures of higher-order interactions and support the search for universal principles governing the organization of group mechanisms across scales.
Fields of science (EuroSciVoc)
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CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
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Project’s keywords as indicated by the project coordinator. Not to be confused with the EuroSciVoc taxonomy (Fields of science)
Programme(s)
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Multi-annual funding programmes that define the EU’s priorities for research and innovation.
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HORIZON.1.2 - Marie Skłodowska-Curie Actions (MSCA)
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Calls for proposals are divided into topics. A topic defines a specific subject or area for which applicants can submit proposals. The description of a topic comprises its specific scope and the expected impact of the funded project.
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Funding scheme (or “Type of Action”) inside a programme with common features. It specifies: the scope of what is funded; the reimbursement rate; specific evaluation criteria to qualify for funding; and the use of simplified forms of costs like lump sums.
HORIZON-TMA-MSCA-PF-EF - HORIZON TMA MSCA Postdoctoral Fellowships - European Fellowships
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Call for proposal
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(opens in new window) HORIZON-MSCA-2025-PF
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08007 BARCELONA
Spain
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