Nontopological scalar soliton as dark matter halo

Galactic dark matter can be modeled by a scalar field coupled to standard gravity in order to effectively modify Kepler's law. In particular, we show that a solvable toy model with a self-interaction U(Φ) borrowed from nontopological solitons produces already qualitatively correct rotation curves. Although the relativistic effects in the halo are very small, our generally relativistic formulation aids at reconstructing more realistic scalar models with self-interaction.