# SKM 2023 – wissenschaftliches Programm

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# DY: Fachverband Dynamik und Statistische Physik

## DY 5: Fluid Physics: Turbulence and Convection

### DY 5.3: Vortrag

### Montag, 27. März 2023, 10:15–10:30, MOL 213

**Spontaneous symmetry breaking for extreme vorticity and strain in the three-dimensional Navier-Stokes equations** — •Timo Schorlepp^{1}, Tobias Grafke^{2}, Sandra May^{3}, and Rainer Grauer^{1} — ^{1}Institute for Theoretical Physics I, Ruhr-University Bochum, Germany — ^{2}Mathematics Institute, University of Warwick, United Kingdom — ^{3}Department of Mathematics, TU Dortmund University, Germany

We investigate the spatio-temporal structure of the most likely configurations realizing extremely high vorticity or strain in the stochastically forced three-dimensional incompressible Navier-Stokes equations. Most likely configurations are computed by numerically finding the highest probability velocity field realizing an extreme constraint as solution of a large optimization problem. High-vorticity configurations are identified as pinched vortex filaments with swirl, while high-strain configurations correspond to counter-rotating vortex rings. We additionally observe that the most likely configurations for vorticity and strain spontaneously break their rotational symmetry for extremely high observable values. Instanton calculus and large deviation theory allow us to show that these maximum likelihood realizations determine the tail probabilities of the observed quantities. In particular, we are able to demonstrate that artificially enforcing rotational symmetry for large strain configurations leads to a severe underestimate of their probability, as it is dominated in likelihood by an exponentially more likely symmetry-broken vortex-sheet configuration.