arXiv subjects

Sarah Sab

Publications and source records attributed to Sarah Sab.

3 recordsLinked to original sources

arXiv2026

Universal scaling and relaxation in decaying turbulence of Bose gases

Understanding the relaxation dynamics of isolated quantum systems remains a central challenge in nonequilibrium physics. In this short review, we discuss recent experimental and theoretical advances in universal dynamics of turbulent Bose gases, with particular emphasis on nonthermal fixed points and wave turbulence in our experimental system at the S\~ao Carlos Institute of Physics of the University of S\~ao Paulo. We highlight the emergence of self-similar scaling behavior and its connection to particle and energy transport across momentum scales. In addition, we discuss an approach in which a differential equation has a universal scaling solution, providing a practical framework for extracting universal exponents from limited regions of the momentum distribution. Furthermore, we recap experimental observations of direct and inverse cascades in a three-dimensional trapped Bose--Einstein condensate, revealing distinct relaxation stages governed by universal scaling laws. These results demonstrate that turbulence plays a key role in far-from-equilibrium dynamics, offering a unified perspective on transport processes and thermalization in quantum many-body systems.

cond-mat.quant-gas↗

arXiv2026

Universal Behavior on the Relaxation Dynamics of Far-From-Equilibrium Quantum Fluids

Investigating the initial conditions that lead many-body quantum systems to an out-of-equilibrium state is fundamental for understanding their thermalization dynamics. In this work we observe the relaxation for two regimes of excitation that can drive the turbulent Bose-Einstein condensate into two distinct final states, and are defined by the amount of energy injected into the system. The subcritical regime is characterized by a lower injection of energy, which can lead to an inverse particle cascade and, consequently, to the BEC mode repopulation during the relaxation process. The supercritical regime is marked by a higher energy injection, that may lead to the BEC dissolution and a final thermal state. In both cases we observe relaxation stages that exhibit the same key features: a direct cascade, a non-thermal fixed point with the same exponents, a prethermalization region and, finally, the thermalization of the system. In the final thermalization stage, universal scaling is observed for both regimes, even though their final states are completely different. By analyzing the coherence length of our turbulent cloud, we clearly visualize the recovery and the loss of the coherence for the subcritical and supercritical regimes after relaxation. These results indicate that the evolution of turbulence occurs independent of its initial conditions and of the final state achieved.

cond-mat.quant-gas↗

arXiv2025

Evolution of density variations in a trapped atomic superfluid driven into turbulence

In this work, we study the free decay of a turbulent trapped Bose gas by analyzing the temporal evolution of density variations extracted from absorption images. We introduce a parameter $\delta$ as a simple and experimentally accessible observable that captures the amplitude of density variations. After the driving is turned off, this parameter exhibits a clear decay, which enabled us to identify a characteristic relaxation time. Interestingly, this timescale remains nearly constant across the range of excitation amplitudes explored, while the magnitude of $\delta$ varies with the injected energy. Numerical simulations based on the Gross-Pitaevskii equation reveal a qualitatively similar behavior, both showing a decay of density variations over time.

cond-mat.quant-gas↗