Journal of the Korean Physical Society (2025) 87:430–440
https://doi.org/10.1007/s40042-025-01420-8
Hyeonmo Koo
Received: 20 August 2024 / Revised: 2 June 2025 / Accepted: 12 June 2025 / Published online: 1 July 2025
© The Korean Physical Society 2025
Abstract
We perform head-on collision simulations of compact dark matter subhalos using distinct numerical methods for fuzzy dark
matter (FDM) and cold dark matter (CDM) models. For FDM, we solve the Schrödinger–Poisson equations with a pseudospectral
solver, while for CDM, we utilize a smoothed particle hydrodynamics N-body code. Our results show that velocity
decrease of subhalos is significantly greater in FDM model than in CDM, particularly at lower initial velocities, attributed
to gravitational cooling—a unique mechanism of stabilizing in FDM with dissipating kinetic energy. This stark contrast in
energy dissipation between two DM models suggests that FDM may offer valuable insights into understanding the dynamic
behaviors of DM during galaxy cluster collisions, such as those observed in the Bullet cluster and Abell 520. These findings
strongly suggest that FDM is not only capable of explaining these complex astrophysical phenomena but also serves as a
compelling alternative to the traditional CDM model, offering resolutions to longstanding discrepancies in DM behavior.
Keywords Fuzzy dark matter · Gravitational cooling · Subhalo · Head-on collision
