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A: Fachverband Atomphysik

A 26: Poster – Ultracold Matter (joint session Q/A)

A 26.3: Poster

Mittwoch, 4. März 2026, 17:00–19:00, Philo 2. OG

Universal scaling and emergent symmetries in a spin-1 Bose gas far from equilibrium — •Ido Siovitz, Anna-Maria E. Glück, Yannick Deller, Helmut Strobel, Markus K. Oberthaler, and Thomas Gasenzer — Kirchhoff Institute for Physics, Universität Heidelberg

Quantum many-body systems driven far from equilibrium can show universal self-similar scaling dynamics associated with an approach to a non-thermal fixed point. The characterisation of non-equilibrium universality classes remains an open problem. Here we show the thorough investigation of non-equilibrium universality using the spin-1 Bose gas as a platform. We identify rogue waves in the velocity fields of the single components, leading to real-time instantons in the transverse spin degree of freedom. We derive a low-energy effective field theory of the spin-1 gas, taking the form of a double sine-Gordon model for the spinor phase. This model accounts for the subdiffusive and diffusion-type scaling observed in the full microscopic theory. We show Numerical as well as experimental results that support the validity of the effective model. Lastly, we demonstrate that different quenches can lead to two distinct non-thermal fixed points, each associated with a different emergent symmetry signaled by symmetry witnesses derived from Ward identities.

Keywords: Far from equilibrium; Universality; Spin-1 Bose gas; Ultracold atoms; Numerical simulation