The ?C?M cosmology offers a picture for galaxy formation that is broadly promising but difficult to reconcile with the evidence that galaxies were assembled earlier than seems naturally to follow from this cosmology, and that environment has had strikingly little effect on the evolution of ellipticals and pure disk spiral galaxies after assembly. Reconciliation might be aided by adding to ΛCDM evanescent matter that has an evolving mass and a fifth force large enough to aid earlier assembly of more nearlyisplated protogalaxies.
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