This paper investigates static, spherically symmetric stellar configurations within non-linear f(R,T)=R+λ(κ2T)n gravity. Due to the analytical complexity introduced by non-linear trace couplings, an effective fluid reformulation is introduced that maps the theory directly into an Einstein-like form. This framework allows for exact parametric solutions across arbitrary values of n for effective constant density fluids and quark-matter-type equations of state. For self-similar configurations, we show that solutions can be found for certain constant equation-of-state in some intervals of n. The models reveal that non-linear matter-geometry couplings alter internal pressure and energy density profiles while preserving compactness bounds closely aligned with the classical Buchdahl limit.
This Comment clarifies the physical interpretation of the black hole spacetime metric employed by Shaymatov et al. [Phys. Dark Univ. 34 (2021) 100891]. We point out that the metric, originally derived in Li and Yang (2012), describes a specific dual-component system consisting of cold dark matter and a phantom field background. Treating this geometry as a single-component “Perfect Fluid Dark Matter” (PFDM) with a total equation of state w_total = -1 is physically incompatible with the gravitational attraction required for dark matter halos. Furthermore, we clarify the distinct parameter regimes of the original model to prevent potential misapplications in extreme astrophysical scenarios.
