Dr Armand Leclerc

Dr Armand Leclerc obtained a bachelor's and master's degree in theoretical physics at the École Normale Supérieure (ENS) de Lyon. He discovered astrophysics at the Centre de Recherche Astrophysique de Lyon with Guillaume Laibe, and, thanks to a 6-month internship in Exeter on high-resolution hydrodynamical simulations, with Isabelle Baraffe. While his PhD project at CRAL together with ENS focused on wave topology in stars and asteroseismology, his background favored connections between astrophysics and other disciplines, for instance, applied mathematics, theoretical cosmology, quantum physics, or condensed matter. He obtained his PhD in the short period of three years, with five first-author papers, and is now postdoc at ISTA, in Austria.

Dr Leclerc's work stands out for its groundbreaking interdisciplinary reach, connecting fundamental concepts borrowed from condensed matter physics with stellar astrophysics in an unprecedented way. At the core of his PhD lies a transformative idea: bringing topological physics (a framework originally developed for quantum and condensed matter systems) into the realm of asteroseismology. This pioneering concept of Topological Asteroseismology unveiled the topological nature of some stellar oscillation modes, providing an entirely new perspective on their probing power of the structure and dynamics of stars. In particular, he demonstrated that some prograde oscillation modes, and the solar f-mode, carry topological signatures that can be exploited to probe the internal dynamics of stars. Dr Leclerc has opened a new diagnostic avenue for constraining stellar rotation and angular momentum transport - an enduring problem in stellar evolution theory.

Dr Leclerc actively built bridges between theory, simulations, and observations for his theoretical works to achieve their full impact. In collaboration with experts in 3D numerical modeling, he demonstrated the feasibility of detecting deep solar oscillation modes sensitive to core properties. This work is already inspiring active searches for these topological signatures in asteroseismic datasets. Such rapid translation from theory to observational investigation underscores his rare ability to communicate complex ideas across disciplinary boundaries and to inspire collaborative work. His work lays the foundation for future applications of topological methods beyond the Sun, extending to other stars, to planetary seismology, and to magnetohydrodynamic waves in astrophysical fluids.

The work was conducted at the Centre de Recherche Astrophysique de Lyon (France)