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MON: Monday Contributed Sessions
MON 15: Many-Body Quantum Dynamics II
MON 15.2: Talk
Monday, September 8, 2025, 16:45–17:00, ZHG003
Equilibrium, Relaxation and Fluctuations in homogeneous Bose-Einstein Condensates: Linearized Classical Field Analysis — •Nils A. Krause1,2 and Ashton S. Bradley1,2 — 1Department of Physics, University of Otago, Dunedin, New Zealand — 2Dodd-Walls Centre for Photonic and Quantum Technologies
We present a thorough analysis of the linearized stochastic projected Gross-Pitaevskii equation (SPGPE) describing finite temperature in Bose-Einstein condensates (BECs). Our study reveals an optimal choice for the cut-off that divides the Bose gas into a low energy coherent region forming a classical wave and a high energy thermal cloud acting as a reservoir. Moreover, it highlights the relevance of energy damping, the number conserving scattering between thermal and coherent atoms. We analyze the equilibrium properties and near equilibrium relaxation of a homogeneous BEC in one, two and three dimensions at high phase space density. Simulations of the full nonlinear SPGPE are in close agreement, and extend our arguments beyond the linear regime. Our work suggests the need for a re-examination of decay processes in BECs studied under the neglect of energy damping.
Keywords: BEC; cold atoms; coherent matter waves; open quantum systems; thermalization