Abstract The cusp–core problem remains a challenge to the ΛCDM model, since dwarf galaxies often exhibit flat central density cores rather than the steep cusps ( ρ ∝ r −1 ) predicted by collisionless N -body simulations. We model the dark-matter-dominated dwarf irregular galaxy DDO 168 within the Bose–Einstein condensate (BEC) or fuzzy dark matter (FDM) framework, in which ultralight bosons form a solitonic core governed by the Gross–Pitaevskii–Poisson (GPP) equations, with the soliton mass–radius relation enforced. We numerically validate the ground-state solution of the GPP system as a consistency check and fit the inner rotation curve of DDO 168 using SPARC data. Within this framework, the data are consistent with an axion mass m = ( 1 . 3 − 0.2 + 0.3 ) × 1 0 − 23 eV , and yield a solitonic core with characteristic radius R c = 2.4 0 − 0.24 + 0.22 kpc , enclosing a mass M (<2.47 kpc) ≃ (1.5 ± 0.2) × 10 9 M ⊙ . The observed flat inner rotation curve is reproduced and the presence of a weak H i bar is compatible with multigigayear survival timescales, consistent with reduced Chandrasekhar dynamical friction in a shallow central potential. These results demonstrate that the BEC/FDM framework provides an internally consistent description of DDO 168, simultaneously reproducing the observed rotation curve, alleviating the cusp–core tension, and allowing long-lived weak bars under conservative dynamical assumptions.
Khanal et al. (Thu,) studied this question.