Mainz 2026 – scientific programme
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A: Fachverband Atomphysik
A 40: Ultra-cold Atoms, Ions and BEC V (joint session A/Q)
A 40.2: Talk
Friday, March 6, 2026, 11:30–11:45, N 1
Hybrid van Hove approach to mixed quantum-classical gases — •Maja Maschke1,2 and Sebastian Ulbricht1,2 — 1Institut für Mathematische Physik, Technische Universität Braunschweig, Braunschweig, Germany — 2Fundamental Physics for Metrology, Physikalisch-Technische Bundesanstalt PTB, Braunschweig, Germany
In cold matter physics, the search for effective approximation schemes is a constant one due to the difficulty of many-particle calculations at the fully quantum level. One set of such schemes are semi-classical approaches in which one sector of a quantum system is treated classically. Historically, such hybrid theories have often been proposed ad-hoc, rather than being derived from a set of first principles. Recently, an axiomatic approach to mixed quantum-classical systems based on a Hilbert space formulation of classical mechanics due to van Hove has been proposed [1]. To date, the consistency of this novel approach was demonstrated at the few-particle level only. In this talk, we extend this work to many-particle systems and discuss its applicability to cold bosonic gases. We will demonstrate how to derive a mean field theory of an interacting hybrid gas at finite temperature featuring a quantum ground state (BEC) and a classical thermal cloud. We present a quantitative analysis of the critical temperature and the condensate fraction and compare our self-consistent numerical approach to the well-established ZNG theory. Our results mark a successful consistency check for the hybrid van Hove-formalism and illustrate to which extent a purely classical description of the thermal cloud is sufficient.
[1] M. Reginatto et al 2025 J. Phys.: Conf. Ser. 3017 012037
Keywords: hybrid system; BEC; ZNG; van Hove; simulations