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Focusing dynamics of 2D Bose gases in the instability regime

Lea Boßmann, Charlotte Dietze and Phan Thành Nam

Vol. 19 (2026), No. 2, 281–316
Abstract

We consider the dynamics of a 2D Bose gas with an interaction potential of the form N2β1w(Nβ ) for β (0, 3 2). The interaction may be chosen to be negative and large, leading to the instability regime where the corresponding focusing cubic nonlinear Schrödinger equation (NLS) may blow up in finite time. We show that to leading order, the N-body quantum dynamics can be effectively described by the NLS prior to the blow-up time. Moreover, we prove the validity of the Bogoliubov approximation, where the excitations from the condensate are captured in a norm approximation of the many-body dynamics.

Keywords
Bose–Einstein condensate, effective evolution equations, focusing NLS
Mathematical Subject Classification
Primary: 35Q55, 81V73
Milestones
Received: 14 February 2024
Revised: 2 December 2024
Accepted: 2 February 2025
Published: 22 January 2026
Authors
Lea Boßmann
Department of Mathematics
Friedrich-Alexander-Universität Erlangen-Nürnberg
Erlangen
Germany
Charlotte Dietze
Laboratoire Jacques-Louis Lions
Sorbonne Université
CNRS
Paris
France
Phan Thành Nam
Department of Mathematics
Ludwig Maximilian University of Munich
Munich
Germany

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