Quantum undular bores, rainbows, and event horizons in superfluid dam breaks
Abstract
The sudden removal of a potential barrier from a Bose-Einstein condensate (BEC) gives rise to a quantum version of a hydrodynamic dam break and leads to rich wave dynamics that have similarities to other localized defect problems such as domain wall dynamics in spin systems. Denoting Δn as the initial difference in density between the upper n1 and lower n0 reservoirs on either side of the dam, we use the Gross-Pitaevskii equation to study the quasi-one dimensional case in both perturbative (Δn ≪ n0) and non-perturbative (Δn ∼ n1) regimes. In the perturbative regime a pair of outwardly propagating dispersive wavepackets forms which can be viewed as quantum versions of undular tidal bores that have analytic forms at long times in terms of the integrals of Airy functions with a wavelength that grows as (ℏ2 t)1/3. Airy functions are the universal wave functions that dress structurally stable fold caustics where pairs of rays coalesce, and, indeed, we show that the quantum dam break problem has the same ray structure as the naturally occurring caustic phenomenon of a double rainbow, including Alexander's dark band between the two bows where no light is scattered: we identify the intermediate density plateau in the dam break as an analogous `silent band' where only evanescent sound waves can exist. In the opposite regime of a non-perturbative dam break we show that a self-induced sonic horizon occurs when Δn ≥ (8/9)n1. A discussion of possible experimental schemes for amplification of quantum undulations is included as well as an alternative scheme for dispersive wave generation where a constant flow is imprinted on a BEC in box trap.
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BibTeX
@misc{farrell2026quantum,
title = {{Quantum undular bores, rainbows, and event horizons in superfluid dam breaks}},
author = {Liam M. Farrell and Wyatt Kirkby and Alex Harris and David Tyler and Maxim Olshanii and Duncan H. J. O'Dell},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.32232},
eprint = {2609.32232},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.32232},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Quantum undular bores, rainbows, and event horizons in superfluid dam breaks
AU - Liam M. Farrell
AU - Wyatt Kirkby
AU - Alex Harris
AU - David Tyler
AU - Maxim Olshanii
AU - Duncan H. J. O'Dell
PY - 2026
DA - 2026/09/26
PB - arXiv
DO - 10.48550/arxiv.2609.32232
UR - https://arxiv.org/abs/2609.32232
AB - The sudden removal of a potential barrier from a Bose-Einstein condensate (BEC) gives rise to a quantum version of a hydrodynamic dam break and leads to rich wave dynamics that have similarities to other localized defect problems such as domain wall dynamics in spin systems. Denoting Δn as the initial difference in density between the upper n_1 and lower n_0 reservoirs on either side of the dam, we use the Gross-Pitaevskii equation to study the quasi-one dimensional case in both perturbative (Δn ≪ n_0) and non-perturbative (Δn ∼ n_1) regimes. In the perturbative regime a pair of outwardly propagating dispersive wavepackets forms which can be viewed as quantum versions of undular tidal bores that have analytic forms at long times in terms of the integrals of Airy functions with a wavelength that grows as (ℏ^2 t)^1/3. Airy functions are the universal wave functions that dress structurally stable fold caustics where pairs of rays coalesce, and, indeed, we show that the quantum dam break problem has the same ray structure as the naturally occurring caustic phenomenon of a double rainbow, including Alexander's dark band between the two bows where no light is scattered: we identify the intermediate density plateau in the dam break as an analogous `silent band' where only evanescent sound waves can exist. In the opposite regime of a non-perturbative dam break we show that a self-induced sonic horizon occurs when Δn ≥ (8/9)n_1. A discussion of possible experimental schemes for amplification of quantum undulations is included as well as an alternative scheme for dispersive wave generation where a constant flow is imprinted on a BEC in box trap.
ER -