Séminaire Général de Physique

"Séminaire Général de Physique"

AMPHI PGG
Bâtiment Condorcet, niveau -1
(café à partir de 10h10)

Prochain séminaire : Kamran Behnia (LPEM-CNRS- Sorbonne Université, ESPCI-PSL) - Vendredi 11 avril 2025, 10h30

Titre : Bacterial Superheroes - An Introduction to Mechano-Micro-Biology

Résumé :

We all have, in all likelihood, more bacterial cells in us and on us than our own cells. While we have studied bacteria in the lab mostly in extremely rich environments where they swim freely, we now understand that most bacteria are part of highly dense, physically interconnected aggregates with limited resources at their disposal. Many bacteria bear appendages called Type IV pili. These long retractable polymers enable bacteria to exert forces on their surroundings and between each other. We will show how the characterization of the forces exerted by these ubiquitous bacterial nanonomachines and their dynamics, across evolution, provides an insightful framework to study the impact of mechanical cues on bacterial physiology.

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Rendez-vous pour le café à partir de 10h10 - Amphithéâtre Pierre-Gilles de Gennes :
Bâtiment Condorcet - Espace de convivialité du niveau -1 (en bas de l'escalier à vis)
10, rue Alice Domon et Léonie Duquet
Université Paris Cité - UFR de Physique Paris 13ème

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Dernier séminaire : Kamran Behnia (LPEM-CNRS- Sorbonne Université, ESPCI-PSL) - Vendredi 14 mars 2025, 10h30

Titre : How sound carries heat in solids

Résumé :

Heat travels in solids thanks to phonons, quanta of lattice waves. The best conductors of heat at room temperature are not noble metals, but carbon-based insulators and semi-metals, such as diamond and graphene/graphite. Near the Debye temperature (the highest lattice energy scale), thermal conductivity is governed by phonon-phonon collisions. At cryogenic temperatures, phonons become ballistic, travelling between sample boundaries. The thermal conductivity has opposite temperature dependences in these two extreme limits and therefore, thermal conductivity peaks at an intermediate temperature. Near this peak, there are hydrodynamic regimes of phonon transport in which the viscosity of the phonon fluid plays a prominent role.
The talk is devoted to recent experiments detecting these regimes in a variety of insulators, such as strontium titanate [1], black phosphorus [2], diamond [3], antimony [4] and sapphire (Al2O3) [5], as well as the connection between this physics and the puzzle of phonon thermal Hall effect [6].

Antépénultième séminaire : Sébastien Charnoz (IPGP- UPC-CNRS) - Vendredi 14 février 2025, 10h30

Titre : Origin of the Earth's Moon

Résumé :

How did our Moon form, and when? What evidence supports its origin? While it is often said that the Moon formed from a giant impact, many mysteries remain unsolved. Even today, no single explanation fully aligns with both astronomical and geophysical data. I will review what we currently know about the Moon’s formation, explore the different possible scenarios and their challenges, and discuss the critical new data needed in the future to better constrain the origin of our Moon. I will also present recent multidisciplinary developments at the interface between astrophysics and geophysics.

Lors des derniers Séminaires Généraux de Physique nous avons reçu :