naXys Newsletter – September 2021

After four years of existence as a research institute, naXys underwent its first external evaluation at the beginning of 2021. Foreign experts have all emphasized the high interdisciplinary nature of the Institute, its unique mix of methodological and thematic expertise, its good international visibility, and the high quality of its scientific production. The results of the external evaluation were presented to the Research council and the CA of the University, who reaffirmed their confidence in naXys.

Congrats to all of us for this excellent performance!

Anne-Sophie Libert
Director of naXys


  • Live or die: Controlling the fate of cells in a tissue in real time using feedback-control microscopyLucien Hinderling (University of Bern), September 30, 13:00 – 14:00, S01
  • The Master Stability Function for synchronization in simplicial complexes, Luca Gallo (University of Catania & Université de Namur), October 14, 13:00 – 14:00
  • Detecting planetary-mass primordial black holes with resonant electromagnetic gravitational-wave detectors, Nicolas Herman (Université de Namur), November 9, 13:00 – 14:00

Abstracts can be found on our website:


  • Journée des Instituts, October 5, UNamur. More information
  • Introduction to Git, Juan Cabrera, October 15, 14:00-16:00, UNamur. Lecture open to all naXys researchers. More information
  • BeNet21 – Belgian Network Research Meeting, November 18, UNamur. The 10th edition of the Belgian Network Research Meeting (BENet) will be organised by the naXys Institute at the University of Namur (UNamur). The keynotes speakers, Ginestra Bianconi (Queen Mary University of London) and Alice C. Schwarze (University of Washington), will deliver their talks online. The purpose of this annual event is to foster communication predominantly among Belgian researchers employing network science on their work, regardless of their discipline: sociology, economics, communication, history, biology, physics, medicine, computer science, mathematics and more. More information



A recent work on ecological networks involving naXys researchers Camille Carpentier, Jürg Werner Spaak and Frederik De Laender has been published in the prestigious journal Nature Ecology & Evolution. More information

“An important question in ecology is to understand how an ecological network’s properties determine its capacity to cope with disturbances. An ecological network can easily be characterised by its number of species (nodes) and the number of interactions between them (edges). The relationship between these two properties has been studied extensively, as well as their influence on ecosystems’ ability to cope with disturbances. However, the mathematical connection between these properties has remained elusive.

Based on the degree distribution of ecological networks, we reinterpret the edge-node relationship as a network-specific (as opposed to universal) property. We show that this relationship is driven by a single parameter b that describes how the number of edges changes when nodes are removed at random from the network. Because of this, b also allows formal expression of the network’s robustness facing such removals. This new robustness expression highlights that there is a trade-off between robustness and the network’s capacity to cope with small changes in species densities (local stability). Analysis of 435 empirical networks through in-silico experiments confirmed these results. Finally, we show how our network-specific approach relates to the classical “universal” approach found in literature. Taken together, our results allow to elucidate the relationship between two complexity and two stability measures, reducing the dimensionality of the stability-complexity debate.”

DETECTING BLACK HOLES OF THE SIZE OF A TENNIS-BALL WITH HIGH-FREQUENCY GRAVITATIONAL WAVES. An innovative experiment to enable the detection of primordial black holes has been proposed by the naXys researchers Nicolas Herman (PhD student), André Füzfa, and Léonard Lehoucq (Master internship), in collaboration with Sébastien Clesse from ULB. More information

They are offering experimenters a device that could detect the gravitational waves emitted by the merging of (still hypothetical) primordial black holes using a specific metal cavity and suitably immersed in a strong external magnetic field. When the gravitational wave goes through the magnetic field, it generates electromagnetic waves in the cavity. This electromagnetic response give some information about the primordial black holes, for example their mass.

This research paves the way for fundamental research into the origins of our Universe. In addition to primordial black holes, this type of detector could also directly observe the gravitational waves emitted at the time of the Big Bang, and thus probe physics at much higher energies than the ones achieved in particle accelerators.

BEWARE FELLOWSHIP. The results of the call for BEWARE fellowships 2 (BElgian WAllonia REsearcher) has been released last June with good news for naXys. The multi-disciplinary project WALSAT (WALlonia Space Awareness Technology) awarded to naXys researchers Anne Lemaitre, Timoteo Carletti, and Jérôme Daquin in collaboration with the industrial partner Aerospacelab aims to develop innovative approaches, techniques and algorithms in the field of space traffic management and space situational awareness to mitigate the risk of collision among debris and satellites. The successful candidate, Matteo Romano, will join the naXys group in October.

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