We study genuine finite density effects in QCD-like theories with three-dimensional Polyakov-loop effective theories for heavy quarks. These are derived from the full QCD-like theories by combined strong-coupling and hopping expansions. In particular, we investigate the cold and dense regimes of phase diagrams where we expect to find Bose-Einstein-condensation of diquark baryons or a fermionic first-order liquid-gas transition, depending on the gauge group of the theory. In two-color QCD, for example, we observe evidence of a continuous zero-temperature transition to finite diquark density when the quark chemical potential $mu$ reaches half the diquark mass, i.e. without binding energy. In G$_2$-QCD we observe, in addition to this Silver Blaze onset of diquark density, a second transition in the density towards an exponential increase by roughly $3mu/T$ corresponding to a finite density of G$_2$-nucleons.
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