Japan is a world reference when it comes to video games. Nintendo, Sony, Sega... so many companies that have left their mark on contemporary popular culture. Fanny Barnabé knows this industry well. A lecturer at the Faculté Économie Management Communication sciencesPo (EMCP) and researcher at the CRIDS/NaDI research institute, she specializes in game studies, a field of research devoted to the study of games. After defending her doctoral thesis on videogame détournement in the fictional universe of Pokémon in 2017, she spent a year as a postdoctoral fellow at the Ritsumeikan Center For Game Studies (Ritsumeikan University, Kyoto), the archipelago's largest video game research center. Internationally recognized, the Center is fortunate to host an exceptional and unpublished archive, thanks to a donation from the giant Nintendo.

Many years and research work later, Fanny Barnabé visited Japan once again at the end of May, on an academic mission. The aim: to present the latest work being carried out at UNamur, particularly in edutainment or "serious game"and, she hopes, lay the foundations for new partnerships and student exchanges.

The Faculty of Informatics has long-standing links with the National Institute of Informatics (NII), an internationally recognized research institute located in the heart of Tokyo. Each year, Master's and PhD students from the faculty are hosted there for a period of four to six months to carry out internships and research projects, via a specific collaboration agreement (Memorandum Of Understanding agreement, or MOU). It's an experience much appreciated by students and PhD students alike, on both scientific and human levels.

Gilles Perrouin, researcher and chairman of the Faculty of Computer Science's Research Commission, guides these students through the presentation of their research topic, often focused in the fields of software engineering, artificial intelligence (AI) or, more recently, green AI. "These are research fields that are evolving very quickly", Gilles Perrouin points out. "There's a lot of debate right now around AI's energy consumption. It's a bit of an oxymoron to say that we can do green AI.But we're working on it via the exploration of smarter techniques when looking for promising solutions to avoid resorting to systematic training of the neural network, which is very costly in terms of energy"explains the researcher. The collaboration has led to the exploration of other areas of AI, such as sign language recognition (Professor Benoît Frénay), in addition to topics in formal methods and software engineering (Professors Pierre-Yves Schobbens and Xavier Devroey).

At the heart of the Mathematics Department, Alexandre Mauroy, professor and researcher at the Namur Institute for Complex Systems (naXys), is working with his long-time collaborator and friend Yoshihiko Susuki from the prestigious University of Kyoto on a project co-funded by F.N.R.S and JSPS (Japan) to study dynamical systems. "These are so-called 'non-linear' phenomena that do not respect the rules of proportionality. The equations are therefore very difficult, if not impossible, to solve in practice, explains Alexandre Mauroy. "To get around this problem, we mobilize techniques like operator theory, which we're studying as part of this project." This has the advantage of combining theoretical aspects with practical applications, particularly in the field of electrical distribution networks. "These are complex systems, with slow and fast dynamics. An interesting case for which mathematical tools need to be adapted", continues Alexandre Mauroy. This first positive partnership has already led to research visits between the two countries, and promises new collaborations in the future.

In a related field, Riccardo Muolo has been a postdoctoral fellow at the Institute of Science Tokyo since 2023, after completing a PhD thesis at UNamur under the supervision of Professor Timoteo Carletti. Building on the knowledge acquired during his PhD on network dynamics, Riccardo Muolo is now interested in network synchronization theory, a mathematical model that enables us to understand a wide variety of systems: from fireflies to electrical networks to the functioning of the human brain: "For example, in the brain, abnormal synchronization of neuronal networks is associated with pathologies such as epilepsy or Parkinson's. The recent power grid failure in Spain can also be analyzed through this theory", details the researcher.

Students wishing to spend part of their degree course in Japan have the opportunity to do so, thanks to the various agreements UNamur has signed with Japanese institutions. This is the case with the National Institute of Informatics (NII), but also with Soka University and Sophia University (Chiyoda), with which UNamur has signed framework agreements.

The study of complex systems published in Physical Reviews Letters supports a growing trend that focuses more on analyzing the collective behavior of a system rather than discovering the underlying mechanisms of interaction.

When we observe a flock of starlings swirling through the sky in perfect coordination - a phenomenon known as murmuration - we witness the elegant interplay of individual actions creating collective behavior. In trying to understand these fascinating patterns, researchers can isolate simple rules based on an individual bird's field of view and the distance separating it from its neighbors, but there's always the question of whether the model actually captures the processes driving interactions between birds (Fig. 1).

This is a general problem in complex systems research, which comes down to distinguishing mechanisms (the rules governing interactions) from behaviors (the observable patterns that emerge).

Representative networks of interacting individuals, or nodes, are a good way to study mechanisms versus behaviors. Until now, researchers have focused on pairwise interactions, but many systems also include higher-order interactions between several nodes. The impact of these higher-order mechanisms on behavior has not been clearly established. Thomas Robiglio, from the Central European University in Vienna, and his colleagues, including Maxime Lucas (CR FNRS - UNamur) addressed this question. They considered networks with higher-order interactions and evaluated the resulting behaviors in terms of statistical dependencies between node values.

The researchers identified higher-order behavioral signatures which, unlike their pairwise counterparts, reveal the presence of higher-order mechanisms. Their findings open up new avenues for distinguishing mechanisms and behaviors when studying complex systems - a distinction that is crucial for the study of inference in network science, neuroscience, the social sciences and beyond.

This study is also the subject of a "Featured in Physics" and "Editor's suggestion" article, and a "commentary" article at the journal's request, available on their website in English in full.

The study, entitled "Topology shapes dynamics of higher-order networks" proposes a theoretical framework specifically designed to understand complex higher-order networks where several agents interact at the same time and thus generalize networks with their interactions in pairs. More precisely, the study shows how topology shapes dynamics, how dynamics learns topology and how topology evolves dynamically.

The aim of this work is to introduce physicists, mathematicians, computer scientists and network scientists to this emerging research field, as well as to define future research challenges where discrete topology and nonlinear dynamics mix.

With the data in their possession, the researchers show that real-life complex systems such as the brain, chemical reactions and neural networks can be easily modeled as higher-order networks, characterized by multi-body connections indicating the fact that several elements of the system interact simultaneously.

This international team is convinced that the visibility of their work through this publication in Nature Physics will open the door to new collaborations with other disciplines that rely on network analysis to study real complex systems.

Kudos to the team for this publication!

After a Master's degree in physics (University of Florence, June 1995), Timoteo Carletti pursued his doctoral studies in Florence (Italy) and Paris (France) at IMCCE, finally defending his doctoral thesis in mathematics in February 2000.

He moved to Belgium in 2005, and was hired at the University of Namur as a lecturer, then as a professor (2008), and finally as a full professor (2011) in the Mathematics Department of the Faculty of Science. In 2010, he was one of the founders of the Namur Center for Complex Systems (now the Namur Institute for Complex Systems - naXys), which he headed until December 2014.

This article is taken from the "Impact" section of the December 2024 issue of Omalius magazine.

On the night of January 31, 1953, the North Sea suddenly rose by almost four meters, submerging parts of the Netherlands and Belgium. The disaster caused the death of over 2,500 people, as well as considerable damage. According to Anna Kiriliouk, lecturer in statistics at UNamur's Department of Mathematics and EMCP Faculty, this exceptional event truly marked "the beginning of the development of extreme value theory, with the development of the first extreme value construction project"

The Delta Plan, as it is called, is a system of dikes that protects the Netherlands against the risk of flooding, with these dikes overtopping once every 10,000 years. A rare danger, certainly, but not zero, which "could not have been calculated using conventional statistics, which are very poorly adapted to rare events", believes the mathematician.

While climate change is often discussed in terms of averages, such as rising temperatures and sea levels, it also has the consequence of increasing the frequency of extreme weather events, with significant repercussions for our societies. "In other words, the risk increases along with the concentration of greenhouse gases (GHGs) in the atmosphere", summarizes the researcher. "Thus, a flood calculated in 1953 to occur only every 10,000 years does not have the same significance as today. The latter could happen more frequently, for example every 1,000 years."

While extreme weather events are on the increase, it's difficult in practice to attribute any particular flood or drought to climate change. With this in mind, Anna Kiriliouk has just been awarded an interdisciplinary research project,named EXALT, in collaboration with UCLouvain. "It involves both climatologists and statisticians, she reveals.

In practice, the EXALT project will therefore calculate the probabilities of an extreme event occurring, and compare this probability with that of the same situation in a world where GHG emissions would not have increased. "Of course, we don't have real data from such a world", says Anna Kiriliouk. "We are therefore basing ourselves on alternative climate simulations, the quality of which we will moreover compare, with a focus on extreme events."

Divided into three working groups, the EXALT project will seek in particular to determine the role of climate change in the occurrence of floods, as well as heat waves and drought in Europe. And to do so as realistically as possible: "One of the things we want to incorporate into climate models concerns the dependency between data," explains Anna Kiriliouk. "For example, if a heat wave hits Namur, there's a good chance that the same temperatures will affect Louvain-La-Neuve. We therefore say that there is a strong spatial dependency between these two data. However, this dependence is probably not at all valid for rain, which is much more heterogeneous. By taking into account all these variables, both spatial and temporal, we hope to improve existing models."

A third working group will study much more distant areas, located in Antarctica. "Until 2016, the extent of the Antarctic ice pack was increasing, before abruptly decreasing", the researcher illuminates. "Or, according to the models, this event was considered almost impossible. But with one of EXALT's partners, we began to analyze the evolution of pack ice extent using extreme value theory. With the latter, this sudden drop was no longer so improbable. This gave us confidence in our approach, which is all the more important when the state of the pack ice has such a strong influence on other climate variables."

This interaction between several climatic processes is, moreover, the subject of a second project just obtained by Anna Kiriliouk and funded by an FNRS Mandat d'Impulsion Scientifique. "The aim is to make it possible to study what we call compound events", explains the researcher. "During extreme climatic situations, we usually associate very high or low values simultaneously, such as a lack of rain and high temperature, resulting in an intense drought. But in the case of compound phenomena, we find that the combination of several variables, albeit in a moderate state, results in a severe and unusual event."

In 2017, for example, Hurricane Sandy, which struck the US coastline, is considered a compound event. While North Atlantic hurricanes usually dissipate in mid-ocean, this one coincided with onshore winds and a high tide, leading to massive flooding of New York and the surrounding area.

"In this project, we will therefore try to include more flexibility between the different variables, by introducing different degrees of dependence, the mathematician elaborates. "We're also going to try, as a second step, to group the dependencies together, in order to lighten the models, which become more and more complex as we add nuances to them. And once these models have been modified, we'll apply them to recent events to test their realism."