Namur Institute For Complex Systems

Denis Langevin (Université Clermont Auvergne)
2025-09-10 13:00 - 14:00 (Europe/Brussels)
Title: Global optimization for inverse design in nanophotonics
Abstract:

Global optimization algorithms for the inverse design of nanophotonic structures is a tool which is providing increasingly convincing results – even though the wave nature of photonic behaviours makes them particularly complex. In the meantime, the field of global optimization itself is rapidly evolving but is prone to reproducibility problems, making it harder to identify the right algorithms to use.
In this talk, I will provide a physicist’s insight into the specificities about photonic problems, and how they help or hinder us when using optimisation tools. I will present “observables” – such as spontaneous emergence of regularity or consistency curves – which are relevant for judging the reliability of an optimization and the quality of the generated solution. To support this discussion, I will draw on benchmark examples covering a broad range of topics, including 1D, 2D, 3D problems.
References:
[1] Barry, M. A., Berthier, V., Wilts, B.. D., Cambourieux, M.-C., Bennet, P., Pollès, R., Teytaud, O., Centeno, E., Biais, N., and Moreau, A., “Evolutionary algorithms converge towards evolved biological photonic structures,” Scientific reports 10(1), 1–10 (2020).
[2] Sörensen, K., “Metaheuristics—the metaphor exposed,” International Transactions in Operational Research 22(1), 3–18 (2015).
[3] Bennet, P., Langevin, D., Essoual, C., Khaireh-Walieh, A., Teytaud, O., Wiecha, P., and Moreau, A., “An illustrated tutorial on global optimization in nanophotonics,” (2023).
This seminar will take place in Room S08 at the Faculty of Sciences.

Alessandro Moirano (LPAP, ULiège)
2025-10-16 13:00 - 14:00
Title: Io, a natural probe for Jupiter’s atmosphere and magnetosphere – (Some of) Juno’s results on the moon-magnetosphere interaction.
Abstract:

Jupiter hosts persistent and bright auroras, which are driven by the precipitation of particles into its atmosphere, mostly electrons. The presence of Io orbiting in the inner Jovian magnetosphere produce a specific auroral emission on Jupiter, called “footprint”, whose details are determined by the atmosphere and the energy of the precipitating electrons. The latter, in turn, depends on the physical magnetospheric process(es) that accelerates the particles along the magnetic field and towards the planet. Therefore, the footprint – and the aurora in general – wraps information about the atmospheric structure and the energy spectrum of the precipitation. During this talk, we will discuss the recent analyses of the observations performed by Juno, which has been orbiting Jupiter and providing an unprecedented vantage point on its polar regions since 2016. To begin with, the position of the Io footprint is affected by the Io plasma torus, a dense and variable plasma cloud around Io’s orbit that is ultimately produced by the volcanic activity on the moon. We were able to constrain the spatial distribution of plasma near Io thanks to several years of observations with Juno. Moreover, during some of the closest-approach to Jupiter, Juno was able to observe the Io footprint near the planetary limb, which provided a unique opportunity to investigate the relation between the spectrum of the precipitating electrons and the vertical profile of the auroral emission. Lastly, by looking at the absorption in the far-ultraviolet recorded with the Ultraviolet Spectrograph onboard Juno, we aim at estimating the hydrocarbon abundances in the upper layers of Jupiter’s atmosphere.

The seminar mostly presents results driven by observations, interpreted in light of current theoretical models. Infrared, ultraviolet and radio observations, as well as in-situ particle measurements, are the backbone of the talk, although the moon-magnetosphere interaction welcome all types of expertise and observations.

This seminar will take place in Room S08 at the Faculty of Sciences.

Isao Ishikawa (Kyoto University)
2025-10-21 13:00 - 14:00
Title: Finite dimensional approximations of push-forwards on analytic functionals
Abstract:
In this talk, we will introduce JetEDMD, a new theoretical framework as a finite-dimensional approximation of the push-forward on the spaces of analytic functionals.
JetEDMD provides a reasonable modification of Extended Dynamic Mode Decomposition (EDMD) and elucidates new mathematical machinery by combining the structure of reproducing kernel Hilbert spaces with the jet spaces on the state space of the dynamical system.

As applications, I will present methods for the data-driven estimation of equilibrium points and the reconstruction of vector fields from discrete trajectory data with a rigorous convergence result. Finally, I will discuss some current mathematical challenges and future research directions within this framework.

Laura Gagliardi (University of Chicago)
2025-10-22 15:00 - 16:30
Title: Reticular frameworks after the Nobel prize: their application for catalysis and CO2 capture
Abstract:

Following reflection on the 2025 Nobel Prize in Chemistry awarded for advances in metal– organic frameworks (MOFs), this lecture explores how state-of-the-art quantum chemical and classical simulations are driving the discovery of reticular materials. Computation today is not only a tool to rationalize experiments, but increasingly a predictive engine for tailoring functional frameworks.
In the first part of the presentation, I will highlight our integrated computational and experimental study of catalytic MOFs, where post-synthetic modification introduced metal– sulfur active sites [1]. Quantum chemical calculations elucidated how sulfur incorporation modulates the electronic structure and catalytic reactivity of the frameworks. These insights provided a mechanistic understanding of hydrogenation catalysis and guided the design of MOFs with tunable properties.
The second part will focus on covalent organic frameworks (COFs). Thanks to their modular architectures and tunable functionalities, COFs offer a highly versatile platform for CO2 direct air capture. We performed a multiscale investigation of COF-999 and its amine- functionalized precursor COF-999-NH₂, integrating density functional theory, molecular dynamics, and grand canonical Monte Carlo simulations with experimental validation [2]. Our findings highlight subtle energy differences in laterally shifted stackings, intrinsic stacking heterogeneity, and pronounced layer buckling. We found that extensive amine– nitrile hydrogen bonding and persistent pore water lead to undesired polymerization that undermines CO₂ uptake. The predicted presence of water is confirmed by subsequent experiments. These insights point to a single, actionable design rule: exclude retained water by introducing hydrophobic pore environments to maximize CO2 capture efficiency.
[1] H. Xie, M. A. Khoshooei, M. Mandal, S. M. Vornholt, J. Hofmann, L. M. Tufaro, K. O. Kirlikovali, D. A. Grimes, S. Lee, S. Su, S. Reischauer, D. Sengupta, K. Fahy, K. Ma, X. Wang, F. Sha, W. Gong, Y. Che, J. G. Vitillo, J. S. Anderson, J. M. Notestein, K. W. Chapman, L. Gagliardi, and O. K. Farha, Introducing Metal–Sulfur Active Sites in Metal–Organic Frameworks Via Post-Synthetic Modification for Hydrogenation Catalysis, Nature Chemistry, 2025. DOI: 10.1038/s41557-025-01876-y
[2] H. Daglar, Z. Zhou, R. Zhu, P. Parihar, J. I. Siepmann, O. M. Yaghi, L. Gagliardi Discovery of Stacking Heterogeneity, Layer Buckling, and Residual Water in COF-999-NH₂ and Implications on CO2 Capture Submitted (2025)

This seminar will take place in Room S05 at the Faculty of Sciences.

Serge Nicaise (Université de Valenciennes)
2025-11-27 13:00 - 14:00
Title: Stability results of dissipative systems via the frequency domain approach
Abstract:

The frequency domain approach goes back to J. Prüss [Trans. Amer. Math. Soc. 284 (1984), 847-857] and F. L. Huang [Ann. Differential Equations 1 (1985), 43-56] that show that a C0 semigroup (etA)t≥0 of contractions in a Hilbert space H is exponentially stable if and only if the resolvent of A is uniformly bounded on the imaginary axis. Afterwards Z. Liu and B. Rao, [Z. Angew. Math. Phys. 56 (2005), 630-644], C. J. K. Batty and T. Duyckaerts [J. Evol. Equ. 8 (2008), 765-780], and A. Bátkai, K.-J. Engel, J. Prüss and R. Schnaubelt [Math. Nachr. 279 (2006), 1425-1440] have given some sufficient conditions on the behavior of the resolvent of A on the imaginary axis that guarantee an almost polynomial decay of the semigroup. Finally an optimal result about the polynomial decay was found by A. A. Borichev and Yu. V. Tomilov [Math. Ann. 347 (2010), 455-478]. This approach is a powerful tool for the study of the decay of the semigroup associated with concrete dissipative systems since it reduces to the study of the resolvent on the imaginary axis.
In my talk, I will first recall these two results and then illustrate them on two particular dissipative systems.

This seminar will take place in Room S08 at the Faculty of Sciences.

Frédéric Crevecoeur (UCLouvain)
2026-02-05 13:00 - 14:00
Title:
Abstract:
This seminar will take place in Room S08 at the Faculty of Sciences.

Women and Girls in Science
2026-02-12
The International Day of Women and Girls in Science takes place every 11th of February, following the declaration by the General Assembly of the United Nations on 22nd of December 2015.
This annual event aims at promoting the access of women and girls to science and technology as well as their full and fair participation. It reminds the important role of women in the scientific community and constitutes a great opportunity to encourage girls and young women to participate in the scientific developments.
Our 2026 keynote speakers are
Pr. Roosmarijn Vandenbroucke (University of Gent) and Pr. Nelly Litvak (Eindhoven University of Technology)
More information and registration : https://wgis.unamur.be

Federica Garin (Université Grenoble Alpes)
2026-02-26 13:00 - 14:00

Thomas Koffel (Université Claude Bernard Lyon 1)
2026-04-16 13:00 - 14:00
