RELAQS: Non-thermal fixed points during RELAxation of far-from-equilibrium Quantum gaseS

• Grant number: 24/04637-8
• Support Opportunities: Regular Research Grants
• Start date: October 01, 2024
• End date: September 30, 2028
• Field of knowledge: Physical Sciences and Mathematics - Physics - Atomic and Molecular Physics
• Agreement: ANR
• Principal Investigator: Vanderlei Salvador Bagnato
• Grantee: Vanderlei Salvador Bagnato
• Principal researcher abroad: Hélène Perrin
• Institution abroad: Centre National de la Recherche Scientifique, France
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated researchers: Amilson Rogelso Fritsch ; Arnol Daniel García Orozco ; Gustavo Deczka Telles ; Kilvia Mayre Farias ; Lucas Madeira ; Mônica Andrioli Caracanhas Santarelli ; Patrícia Christina Marques Castilho

Abstract

The RELAQS project joins the efforts of two groups in France and Brazil to explore the relaxation of many-body quantum systems prepared far from equilibrium. While quantum statistical mechanics provides a good description of physical systems in thermodynamic equilibrium, their behavior during relaxation is more challenging to predict from the microscopic model. In the case of far-from-equilibrium initial conditions, universal power laws in the momentum distribution emerge, independent of initial conditions, well before an equilibrium or a quasi-stationary state is reached. This has been investigated in a wide variety of systems such as the inflation in the early Universe, heavy-ion collisions producing quark-gluon matter, and cold-gas systems, both in theory and experiments. A universal spatio-temporal scaling emerges, independent of the initial state or microscopic parameters, suggesting the existence of an underlying physical law. It has been proposed that the universal scaling observed in these far-from-equilibrium isolated systems is due to a relaxation through non-thermal fixed points (NTFP).In this project we will investigate the conditions for the appearance of an NTFP in the relaxation of Bose gases prepared far from equilibrium, with three complementary experimental setups featuring rubidium atoms: a three-dimensional (3D) Bose gas confined in an harmonic trap; a 3D Bose gas in a box potential; and a two-dimensional (2D) Bose gas in an anharmonic shell trap, where curvature can play a role. We will investigate how these gases prepared in a highly out-of-equilibrium turbulent state involving vortices and solitons relax to equilibrium. Experiments will be combined with theory in an effort to identify new ways to evidence universality in the relaxation of the systems. In the 2D shell trap gas we will explore if NTFP also applies in the relaxation of a cloud strongly excited by rotation towards a vortex lattice. The project will increase our understanding of out-of-equilibrium many-body quantum systems and allow us to compare different physical systems in the same universality class. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

MACHADO, L. A.; MADEIRA, L.; CARACANHAS, M. A.; BAGNATO, V. S.. Spectroscopy of collective modes in a Bose-Einstein condensate: From single to double excitation periods. AVS QUANTUM SCIENCE, v. 7, n. 2, p. 13-pg., 2025-06-01. (14/50857-8, 13/07276-1, 23/04451-9, 24/04637-8)