Modified Newtonian dynamics (MOND)

A low-acceleration modification associated with Mordehai Milgrom. For an isolated spherical system, $g\mu (g/a_0)=g_N$, with $\mu (x)\to 1$ at high $x$ and $\mu (x)\to x$ at low $x$. An isolated point-like baryonic distribution then gives $v_c^4=G{M}_b{a}_0$ and a flat asymptotic galaxy rotation curve. The algebraic spherical relation is not a complete relativistic field theory and should not be assumed to hold vectorially for arbitrary mass distributions.^[ref]