Our laboratory is in mourning following the death of our colleague Richard Taillet, who passed away on August 6, 2025, after a sudden illness.
Richard completed his studies as a student civil servant at the École Normale Supérieure de Lyon.
As such, in 1992, he was part of the first graduating class of the DEA (Diploma of Advanced Studies) in theoretical physics in the Rhône-Alpes region. It was therefore quite natural that he joined LAPTh in October 1993 to prepare his doctoral thesis under the supervision of Pierre Salati, having already obtained his agrégation in physical sciences. During his doctoral studies, he focused on the problem of galactic dark matter, and more specifically on the possible presence of faint, low-luminosity stars (brown dwarfs) within globular clusters. He demonstrated, in particular, that these systems could contain, if present, a large population of such stars undetectable by classical observational methods. He suggested new investigative techniques, such as infrared analysis of globular clusters. Richard also showed that galactic dark matter could not be composed of clouds of cold gas, as had been suggested by Françoise Combes and Daniel Pfenniger. Richard defended his thesis in December 1995.
Richard was recruited as a lecturer and researcher at the University of Savoie in 1998, after a 16-month postdoctoral fellowship at the Center for Particle Astrophysics (CfPA) at the University of California, Berkeley. During his time in the United States, he collaborated with Joseph Silk on problems in pure cosmology. He also studied the dispersion of stellar velocities within globular clusters, using the Michie model.
Upon returning to France, he modeled the Large Magellanic Cloud to explain the light amplification events observed through self-lensing of stars in this galaxy. He also worked on the gamma-ray signal produced by the annihilation of dark matter in spheroidal dwarf galaxies, objects known to contain large amounts of dark matter. He participated in the Supernova Collaboration, led by Reynald Pain. This experimental group aimed to determine the matter and energy density of the vacuum by analyzing the relationship between the apparent magnitude and the redshift of type Ia supernovae, veritable standard candles allowing us to probe the universe.
In the late 1990s, Richard, in collaboration with David Maurin and Fiorenza Donato, became interested in cosmic ray antiprotons. These are naturally produced by the collision of cosmic protons and helium nuclei with the gas of the galactic disk. However, they could also be generated by the annihilation of exotic particles, which helps explain dark matter, as their signature is revealed to be an excess of their flux. Such work requires meticulous modeling of the propagation of charged particles within the galaxy’s magnetic fields. This long-term project led to numerous publications as well as the development of the public code USINE, directed by David Maurin.
Richard was also deeply involved in science communication, far beyond our laboratory and university. He demonstrated his exceptional teaching skills, notably through his YouTube channel, the “Le quart d’heure insolite” lecture series, and various television programs.
A passionate researcher and teacher, he had served as Director of the Faculty of Sciences and Mountain Studies at the University of Savoie Mont Blanc since 2021. His teaching led him to publish several books on a wide range of subjects.
We will remember a passionate and dedicated colleague, endowed with great human qualities, who always demonstrated exceptional commitment to our university and science in general.
Richard, we will miss you!
The laboratory and the university will never be the same without your energy, enthusiasm, dedication, passion, and humor.
We are all shocked by this tragic loss, and our thoughts are with his family, especially his partner Laurence.
For those who wish to leave a message or tribute to Richard’s family, texts can be sent to contact@lapth.cnrs.fr. The laboratory will compile a collection of these messages, which will be given to Richard’s loved ones.
