Initial Rotation-Curve Tests of a Constitutive Framework for Gravity: Comparison with MOND in Three Disk Galaxies

We test a constitutive formulation of gravity in the weak-field regime using rotation curves of threerepresentative disk galaxies: NGC 3198, DDO 154, and NGC 2403. The framework introduces a nonlinearresponse function that modifies the relation between the gravitational field and baryonic matter at lowaccelerations. A single acceleration scale a0 is fitted jointly across all galaxies and held fixed in allsubsequent fits.The model successfully reproduces the observed rotation curves using only baryonic inputs, capturingboth the Newtonian inner regions and the flat outer profiles. We compare the results to a standardModified Newtonian Dynamics (MOND) interpolation and find that the constitutive model providessystematically improved agreement across all three galaxies. This improvement is quantified using χ2per data point, which is significantly lower for the constitutive framework in each case.The model also reproduces the observed radial acceleration relation, supporting the interpretationthat galaxy-scale dynamics arise from a modified response in the low-acceleration regime. These resultssuggest that the functional form of the transition between Newtonian and modified regimes plays acentral role in explaining galactic rotation curves.