  Dark Matter (DM) and Modified Newtonian Dynamics (MOND) models of
rotationally supported galaxies lead to curves with different geometries in
$(g_{N},g_{tot})$-space ($g2$-space). Here $g_{tot}$ is the total acceleration
and $g_{N}$ is the acceleration as obtained from the baryonic matter via
Newtonian dynamics. In MOND modified inertia (MI) models the curves in
$g2$-space are closed with zero area and so curve segments at radii $r\geq
r_{N}$ (large radii) and $r< r_{N}$ (small radii) coincide, where $r_{N}$ is
the radius where $g_N$ is greatest. In DM models with cored density profiles
where $g_{tot}$ is also zero at the galactic centre, the curves are again
closed, but the area of the closed curves are in general non-zero because the
curve segments at radii $r\geq r_{N}$ and $r<r_{N}$ do not coincide. Finally in
DM models with cuspy density profiles such as the NFW profile where $g_{tot}$
is formally non-zero at the galactic origin the curves are open, and again the
curve segments at radii $r\geq r_{N}$ and $r< r_{N}$ do not coincide. We
develop a test of whether data at small and large radii coincide and
investigate rotation curves from the SPARC database in order to discriminate
between the above geometries. Due to loosely quantified systematic
uncertainties we do not underline the result of the test, but instead conclude
that the test illustrates the relevance of this type of analysis and
demonstrate the ability to discriminate between the considered DM and MI models
in this way.
