All Years Seminars
[INMA] 2026-01-20 (14:00) : Opinion Dynamics with Nonlinear Interaction: From Robust Clustering to Environmental Coupling
At Euler building (room A.002)
Speaker :
Anthony Couthures (Université de Lorraine)
Abstract : Social opinion and environmental states are deeply coupled: collective human behavior impacts the environment, while the state of the environment feeds back into public opinion. In this talk, I will present a mathematical framework to analyze these interactions, moving from standard consensus models to coupled socio-environmental dynamics.
First, I will introduce a generalized framework for multi-agent opinion dynamics with nonlinear interactions. Unlike classical linear consensus models, nonlinear communication allows for the emergence of rich behaviors beyond simple agreement. We will establish a sharp threshold linking network connectivity (algebraic connectivity) and interaction nonlinearity (Lipschitz constant) that dictates the transition from global synchronization to persistent polarization. Using Input-to-State Stability (ISS) theory, I will also discuss the robustness of these polarized clusters against external influence.
In the second part, I will couple this opinion model with an environmental resource variable. By analyzing the system on the synchronization manifold, we identify the role of the "attention parameter" β: representing the weight agents place on environmental feedback versus social influence. Through bifurcation analysis, I will demonstrate how varying this parameter triggers fundamental qualitative changes, specifically Pitchfork bifurcations (leading to bistability and polarization) and Hopf bifurcations (leading to recurrent cycles of environmental collapse and recovery).
[ELEN] 2026-01-06 (09:00) : Environmental Net Impact of AI - Reviewing Challenges for Decision Making
At Shannon
Speaker :
Daniel Schien (University of Bristol)
Abstract : The net environmental impact of digital services, and artificial intelligence (AI) services in particular, is of increasing interest to society and governance of this part of the economy. The practice of weighing of both positive and negative consequences to arrive at a net impact of digital services has been around for many years and attracted controversy. Efforts such as methodology development through the EU Green Digital Coalition demonstrate ongoing interest as well as the fundamental challenges with this practice. Following a recent pre-print article, I will review existing net-impact methodologies along with the general epistemological challenges and illustrate them through a case study of estimating the benefits from substituting human translation work through LLMs.
[INMA] 2025-12-16 (14:00) : Geometry of low-rank tensors
At EULER (room A.002)
Speaker :
Simon Jacobsson (KU Leuven)
Abstract : Morally, a manifold is a set where notions from calculus are well-defined. For example, the set of n-by-n orthogonal matrices and the set of n-by-n symmetric positive definite matrices are manifolds. Knowing that a set of matrices or tensors is a manifold allows us to use a host of calculus tools to do numerical analysis on that set. For example, many constrained optimization problems can be formulated as unconstrained manifold optimization problems. Algorithms for these can then make use of manifold gradients and analogues of straight lines called geodesics.
We consider the set of fixed-rank tensors. When the rank is sufficiently low, then (almost) any tensor in this set is related to (almost) any other tensor via a change of basis. We explain how this relation induces a manifold structure, and show how relevant quantities like gradients and geodesics can be computed efficiently. More precisely, we identify the set as a quotient of Lie groups. We also discuss how the manifold perspective can be used to integrate tensor differential equations.
[ELEN] 2025-12-16 (16:15) : Acquisition chain vs. value chain: how to reconcile technological innovations and market needs
At BARB91
Speaker :
Thomas Walewyns (ChipsWIN - ICHEC)
Abstract : Dr. Walewyns received the M.Sc. degree in electromechanical engineering and a Ph.D. degree in engineering sciences, both at the Université catholique de Louvain (UCLouvain), Louvain-la-Neuve, Belgium, in 2010 and 2016 respectively. In 2010, he obtained the AILouvain Innovation Award for his master thesis. From 2013 to 2015, he was also carrying out an Executive Master in Management at the Louvain School of Management. Specialized in microsensors, system integration and micro-/nano-fabrication, he is author and co-author of more than 20 scientific articles and conference papers, and holds 3 patents. Passionate about innovation and driven by business, he founded VOCSens, a UCLouvain spin-off developing selective multi-gas microsensors for environmental monitoring & industrial applications, that he managed from 2019 to 2024. He is now leader of ChipsWIN, the Walloon competence centre in semiconductors, strategic advisor for various startups, and part-time guest lecturer at ICHEC.
[ELEN] 2025-12-15 (16:15) : Raw material challenges in photovoltaic technology: entering the terawatt age
At BARB10
Speaker :
Jonathan Parion (University of Hasselt)
Abstract : Jonathan Parion is a PhD student at the University of Hasselt, the University of Ghent and imec. His current work focuses on the characterization and simulation of perovskite thin-film solar cells, specifically to improve their stability and sustainability. Before his PhD, Jonathan followed a master in electrical engineering science at UCLouvain, focusing on device physics and nanotechnology.
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