This work analyzes the residual structure of the radial acceleration relation (RAR) using the SPARC galaxy rotation curve database. After accounting for the leading dependence on halo fraction, a weak but persistent radial structure remains in the RAR residuals. The residual pattern forms a broad transition band around R/Rd ≈ 2.5–3.5 across the disk galaxy sample. The analysis indicates that the apparent tightness of the RAR does not eliminate all internal dynamical structure. Instead, a secondary radial organization appears once the dominant halo contribution is removed. The numerical value π lies within this transition band. This observation is presented as a geometric coincidence rather than evidence of a new dynamical constant. This study does not propose a modification of gravity or a new physical law. The goal is to document a potential internal radial structure in the RAR residual field and to provide a descriptive observational analysis of this feature within the SPARC galaxy sample.
umimoto (Sun,) studied this question.