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Impact of physicality on network structure

Nature Physics volume 20, pages 142–149 (2024)Cite this article

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Abstract

The emergence of detailed maps of physical networks, such as the brain connectome, vascular networks or composite networks in metamaterials, whose nodes and links are physical entities, has demonstrated the limits of the current network science toolset. Link physicality imposes a non-crossing condition that affects both the evolution and the structure of a network, in a way that the adjacency matrix alone—the starting point of all graph-based approaches—cannot capture. Here, we introduce a meta-graph that helps us to discover an exact mapping between linear physical networks and independent sets, which is a central concept in graph theory. The mapping allows us to analytically derive both the onset of physical effects and the emergence of a jamming transition, and to show that physicality affects the network structure even when the total volume of the links is negligible. Finally, we construct the meta-graphs of several real physical networks, which allows us to predict functional features, such as synapse formation in the brain connectome, that agree with empirical data. Overall, our results show that, to understand the evolution and behaviour of real complex networks, the role of physicality must be fully quantified.

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Fig. 1: LPNs.
Fig. 2: Meta-graph and independent sets.
Fig. 3: Predicting node positions in the jammed state.
Fig. 4: Meta-graph of real networks.

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Data availability

Data to generate random LPNs and reproduce the figures are available at https://github.com/posfaim/randLPN.

Code availability

Code to generate random LPNs and reproduce the figures are available at https://github.com/posfaim/randLPN.

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Acknowledgements

This research was funded by ERC grant no. 810115-DYNASNET.

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Author notes

  1. These authors contributed equally: Márton Pósfai, Balázs Szegedy.

Authors and Affiliations

  1. Department of Network and Data Science, Central European University, Vienna, Austria

    Márton Pósfai, Iva Bačić, Luka Blagojević, János Kertész & Albert-László Barabási

  2. Alfréd Rényi Institute of Mathematics, Budapest, Hungary

    Balázs Szegedy, Miklós Abért & László Lovász

  3. Institute of Physics, Belgrade, Serbia

    Iva Bačić

  4. Network Science Institute, Northeastern University, Boston, MA, USA

    Albert-László Barabási

  5. Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA

    Albert-László Barabási

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  1. Márton Pósfai
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Contributions

M.P. developed and performed the simulations. M.P. and B.Sz. derived the analytical results. M.P. and L.B. analysed the empirical data. All authors contributed to the conceptual design of the study and the writing of the manuscript. A.-L.B. was the lead writer of the manuscript.

Corresponding author

Correspondence to Albert-László Barabási.

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Competing interests

A.-L.B. is the founder of Foodome and ScipherMedicine companies that explore the role of networks in health and urban environments. The other authors declare no competing interests.

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Nature Physics thanks Andrea Gabrielli, Zoltán Toroczkai and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–24.

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Pósfai, M., Szegedy, B., Bačić, I. et al. Impact of physicality on network structure. Nat. Phys. 20, 142–149 (2024). https://doi.org/10.1038/s41567-023-02267-1

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