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Projekt Druckansicht

Klassische, quanten und aktive Flüssigkeiten außerhalb des Gleichgewichts

Fachliche Zuordnung Statistische Physik, Nichtlineare Dynamik, Komplexe Systeme, Weiche und fluide Materie, Biologische Physik
Kern- und Elementarteilchenphysik, Quantenmechanik, Relativitätstheorie, Felder
Strömungsmechanik
Theoretische Physik der kondensierten Materie
Förderung Förderung von 2018 bis 2024
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 406818893
 
Erstellungsjahr 2023

Zusammenfassung der Projektergebnisse

Exploring non-equilibrium fluids: turbulence, collective motion in active matter, dark matter and cosmological large-scale structures: Non-equilibrium fluids are ubiquitous in Nature, they appear at all scales, from exciton-polariton gas in semiconductor micro-cavities to cosmological large-scale structures, they involve constituents of very different nature, from inert molecules in a liquid, or atoms in the early universe to living starlings in moving flocks, and they display a large variety of phenomena, from turbulence to structure formations or Bose-Einstein condensation. Yet they share many universal features, and understanding at a theoretical level the emergence and the nature of their statistical properties is the major challenge that the NEQfluids project has addressed. It has specifically focused on the universal properties of incompressible classical fluids in a turbulent state, the phase diagram of active matter, the macroscopic properties of compressible quantum fluids, both in the primordial universe or in condensates of light in microcavities. The functional renormalisation group as the universal key to unravel the statistical properties of non-equilibrium fluids: The NEQfluids project was based on the use of a common unified method, the functional renormalisation group, to tackle the wide variety of problems it addressed. This is a fieldtheoretical approach, which provides a modern and powerful formulation of Wilson’s original ideas. Its key assets are its versatility, it can be adapted to describe both classical, quantum or active fluids, relativistic or not, with diverse interactions, and its ability to tackle strongly coupled, or non-perturbative problems, which are notoriously difficult to treat in general. The project was supported by the strong expertise of all the participants in these techniques, which enabled fruitful exchanges and many advances. The project also led to new methodological developments, such as the deepened use of extended symmetries, or improved approximation schemes, which will benefit the whole fRG community. Main results: A major result was obtained in the theoretical description of turbulent flows, through the precise characterisation of their space-time correlation functions at large wavenumbers. Another breakthrough was to elucidate the genuinely non-equilibrium nature of condensates of polaritons, surprisingly related to Kardar-Parisi-Zhang universality. We also established an extended fluid description of dark matter structure formation beyond shell crossing and found intriguing possibilities to use quantum fluids as quantum simulators for the dynamics in the early universe. For active matter, we uncovered a new universality class describing the interface roughening during phase separation, which differs from both its equilibrium counterpart and its passive analogue. Scientific production: The results of the project were published in 46 international peered-review journals with high impact factors, including 2 Nature, 2 Nature Physics, 6 PRL, 2 EPL, and 1 Phys. Rep. They were presented in more than 50 invited conferences and seminars. The results concerning non-equilibrium exciton-polariton condensates and quantum simulators of early universe were disseminated towards a wide audience through 8 vulgarisation articles. Two numerical codes were produced and made available to the community. The project also led to many theoretical developments valuable for the fRG community.

Projektbezogene Publikationen (Auswahl)

 
 

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