No evidence of vorticity production from irrotational turbulent gravitational collapse yet
Abstract
Gravitational collapse creates large amounts of kinetic energy that could potentially seed turbulence. If such turbulence were also suitable to initiate dynamo action, the resulting magnetic field would further modify the dynamics, especially on small length scales. However, a small-scale dynamo is believed to require vortical turbulence, whereas the collapse produces mainly irrotational motions, which may not be efficient for dynamo action. Here, we study the efficiency of vorticity production during a turbulent collapse. We adopt a barotropic equation of state, where pressure and density gradients are parallel, and no magnetic field, so that vorticity can only be produced by viscosity and by vortex dynamo-type amplification. Using direct numerical simulations of gravitational collapse, we show that, for the parameter space accessible to our numerical resolution, these effects are related to the initial irrotational turbulence and are not induced by the collapse. Vorticity production along with the associated small-scale dynamo action are still expected to occur for sufficiently large Reynolds numbers, especially when baroclinic effects are allowed for, but some of the earlier numerical evidence in the literature using a barotropic equation of state is now found to be the result of subgrid scale modeling and not reproduced in direct numerical simulations.
Versions
Related
- Evidence for Hierarchical Turbulent Scaling in Nearby Star-Forming Galaxies
- Seeing in the Dark: Gravitational Waves from Resonant Production of Dark Photon Dark Matter
- Gravitational Dark Matter Production from Spectator Field in R2-Higgs Inflation
- Universality classes of sharp gravitational production of light particles
- Resonant Gravitational Production of Chiral Dark Photons
BibTeX
@misc{brandenburg2026evidence,
title = {{No evidence of vorticity production from irrotational turbulent gravitational collapse yet}},
author = {Axel Brandenburg and Evangelia Ntormousi and Jennifer Schober},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.01207},
eprint = {2607.01207},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.01207},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - No evidence of vorticity production from irrotational turbulent gravitational collapse yet
AU - Axel Brandenburg
AU - Evangelia Ntormousi
AU - Jennifer Schober
PY - 2026
DA - 2026/10/28
PB - arXiv
DO - 10.48550/arxiv.2607.01207
UR - https://arxiv.org/abs/2607.01207
AB - Gravitational collapse creates large amounts of kinetic energy that could potentially seed turbulence. If such turbulence were also suitable to initiate dynamo action, the resulting magnetic field would further modify the dynamics, especially on small length scales. However, a small-scale dynamo is believed to require vortical turbulence, whereas the collapse produces mainly irrotational motions, which may not be efficient for dynamo action. Here, we study the efficiency of vorticity production during a turbulent collapse. We adopt a barotropic equation of state, where pressure and density gradients are parallel, and no magnetic field, so that vorticity can only be produced by viscosity and by vortex dynamo-type amplification. Using direct numerical simulations of gravitational collapse, we show that, for the parameter space accessible to our numerical resolution, these effects are related to the initial irrotational turbulence and are not induced by the collapse. Vorticity production along with the associated small-scale dynamo action are still expected to occur for sufficiently large Reynolds numbers, especially when baroclinic effects are allowed for, but some of the earlier numerical evidence in the literature using a barotropic equation of state is now found to be the result of subgrid scale modeling and not reproduced in direct numerical simulations.
ER -