Evanescent Matter
  The LCDM cosmology offers a picture for galaxy formation that is broadly
promising but difficult to reconcile with the evidence that environment has had
strikingly little effect on the evolution of ellipticals and pure disk spiral
galaxies. Reconciliation might be aided by adding to LCDM an evanescent
component of matter with evolving mass and a fifth force large enough to aid
early assembly of more nearly isolated protogalaxies. I present a simple
illustration.
