Abstract
The connection between star formation and disk instabilities has been an outstanding problem for decades. Surprisingly, both observations and theory have shown that empirical laws of star formation and other phenomena concerning self-regulation of star formation in disks can be explained neglecting completely magnetism. From the dispersion relationship for non-axisymmetric modes and other arguments, we aim to show here the relevance of magnetic fields for galactic-scale star formation in normal spirals and massive protodisks. It is concluded that recent claims that suggest magnetic fields as being responsible for the origin of the Hubble sequence have not any theoretical support yet.
