Alternative approach to the galactic dark matter problem

We discuss scenarios in which the galactic dark matter in spiral galaxies is described by a long range coherent field which settles in a stationary configuration that might account for the features of the galactic rotation curves. The simplest possibility is to consider scalar fields, so we discuss, in particular, two mechanisms that would account for the settlement of the scalar field in a nontrivial configuration in the absence of a direct coupling of the field with ordinary matter: topological defects and spontaneous scalarization.