The focus of this workshop was on the hydrodynamic behavior and its microscopic origin of topological, fractonic and active matter. Phases of matter consist of collective states of particles that have emergent properties beyond their underlying microscopic constituents. They can be divided by the nature of their excitations with vanishing energy. We distinguish gapped systems that do not have excitations as the energy goes to zero and gapless systems with zero energy excitations in isolated points in momentum space. Examples of gapped systems include insulators and quantum Hall states. Gapless systems comprise of semimetals such as graphene and Dirac/Weyl semimetals or certain newly discovered fractonic phases of matter with immobile excitations. Their exotic properties are believed to be at the heart of new generation of electronics (semimetals), novel type of quantum memories (fractons) or future engineering (metamaterials). Ultimately the research goals were to understand the interplay between symmetry, topology and geometry at different scales and connect transport phenomena to microscopic models.
We gathered prominent experimentalists and theoreticians from around the world. The top experimental groups in the field of electronic hydrodynamics were represented by Andrew Mackenzie, Shalal Ilani, Yuan Yan, Jonah Waissman. The main theoretical physicists present included Alexander Abanov, Anton Burkov, Joel Moore, Jörg Schmalian, Igor Shovkovy, Michael Stone and Vincenzo Vitelli.
We had several young researchers present, who reported their results as speakers (Paweł Matus, Jimena Siepe) and in the form of posters. All of the showed scientific maturity and good outreach skills.
The workshop served as a platform to connect communities of condensed matter and high-energy physicists. Both communities are actively investigating hydrodynamic regime of matter. In the high-energy the focus is on heavy-ion collisions and in condensed matter on topological materials and metamaterials. The workshop provided an opportunity to report new technical developments in kinetic theory, hydrodynamics and effective field theories as well as discuss a variety of physical systems and phenomena, in which new transport signatures can be present. As a result researchers will be able to, on the one hand, extend the applicability of the developed formalisms and on the other hand to identify proper theoretical description to the experimentally observed phenomena.