How reliable and empirically backed are the Borde, Guth, Vilenkin models for the origin of the universe?
First of all: Borde, Guth, Vilenkin wrote *together* the articles that expanded on Guth’s cosmological inflation model. So it’s one and the same model. The basic picture of the model makes a number of predictions that have been confirmed by observation. Therefore Inflation is now considered part of the standard big bang cosmology. Cosmological inflation has the important effect of smoothing out any inhomogeneities and anisotropies. Such inhomogeneities are *not* observed but the original Big Bang model didn’t have any means to provide such smoothing. Furthermore Inflation gets rid of exotic, massive particles that a lot of GUTs require to exist. There are cyclic models of the Universe (Big Bangs and Crunches alternate) that can do the same tricks, but less elegantly. Also these models would require the Universe being even more massive than it seems to be.
