  We show that amphiphilic and colloidal systems with competing interactions
can be described by the same Landau-Brazovskii functional. The functional is
obtained by a systematic coarse-graining procedure applied tosystems with
isotropic interaction potentials. Microscopic expressions for the coefficients
in the functional are derived. We propose simple criteria to distinguish the
effective interparticle potentials that can lead to macro- or microsegregation.
Our considerations concern also charged globular proteins in aqueous solutions
and other system with effective short-range attraction long-range repulsion
interactions.

Soft Condensed Matter