One Single Metric Model's Unifying Perspective on Four Issues with Galactic Dynamics: B-TF Relation, Rotation Curves, Spirals and SMBH-Growth

In this paper, we intend to replace four mysteries of galactic dynamics with one. This one mystery is introduced as a postulate: the constant Lagrangian metric as a space-time background for galactic dynamics. The four mysteries of galactic dynamics are the B-TF relation, the rotation curves, the spiral structure and SMBH-growth. Why the galactic space-time background behaves like a giant disk with directionally synchronized metronomes on it (the constant Lagrangian metric) remains an open question.