## Le Jeudi 25 Juin 2020 à 14h00 - par visioconférence

pour y assister contacter L. Pauchard (pauchard@fast.u-psud.fr) ou E. Reyssat (etienne.reyssat@espci.fr).
### Topological waves in geophysical and astrophysical flows

Antoine Venaille

## Laboratoire de Physique - ENS Lyon

Over the last decades, concepts from topology have spread over virtually all fields of physics to explain the emergence of trapped unidirectional modes at the boundary of a system at hand. Topology relates the number of unidirectional modes trapped along interfaces or boundaries to the twisting of bulk modes. Since bulk modes are simple to compute, topology turns a complicated problem into a simpler one. The topological origin of unidirectional waves usually guarantees their robustness against disorder or changes of parameters in the problem. Originally discovered in exotic materials called topological insulators, those ideas have now been applied from cold atoms to photonics or mechanics. We will present recent applications to geophysical and astrophysical fluid dynamics. We will show that topology brings new understanding on equatorial waves encountered in El Nino phenomenon, on oceanic tides, and on internal waves encountered in stably stratified layers of stars.