The hidden gauge theory of relativistic hydrodynamics, and what is a "fluid" of 50 particles?

9 febbraio 2023
Orario di inizio 
PovoZero - Via Sommarive 14, Povo (Trento)
Aula Graziano Fortuna
Organizzato da: 
Comunità universitaria
Ingresso libero
prof. Giorgio Torrieri - Istituto De Fisica Gleb Wataghin, University of Campinas, Brasil


The observation, in hadronic collisions, of "ideal fluid" type behavior in systems of a comparatively small number of particles, presents a conceptual puzzle, since the way we usually derive hydrodynamics is via approximating "many" particles as a
continuum. I will argue that making sense of this requires re-deriving relativistic hydrodynamics as a "bottom-up" theory, with no reference to microscopic physics except the local emergence of a thermalized system. We attempt to do this using
basic statistical mechanics, and find the appearance of a gauge-like redundancy hidden within relativistic dissipative hydrodynamics, arising from the fluctuationdissipation theorem. This might lead to the apparently counter-intuitive conclusion
that in the small viscosity limit it might indeed be that smaller systems could thermalize faster.

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