Spherical scalar field halo in galaxies - art. no. 061301

We study a spherically symmetric fluctuation of scalar dark matter in the c osmos and show that it could be the dark matter in galaxies, provided that the scalar field has an exponential potential whose overall sign is negativ e and whose exponent is constrained observationally by the rotation velocit ies of galaxies. The local space-time of the fluctuation contains a three-d imensional spacelike hypersurface with a surplus of angle.