From Ned Wright's
News of the Universe
Cosmic Ripples instead of Dark Energy?

16 Mar 2005 - Rocky Kolb et al. have suggested that large scale ripples
in space-time could explain the observations of the accelerating
Universe that seem to require dark energy - the vacuum energy density
that is equivalent to the cosmological constant. Despite issuing press
releases and getting some coverage, even in the Los Angeles Times
although 10 days later, I find their arguments lacking. In Einstein's
General Relativity, the local metric determines the local stress-energy
tensor, so the large scale ripples do not change the need for a
negative pressure and hence a vacuum energy density or cosmological
constant based on the supernova observations of the local geometry.

[this article withembedded links:
http://www.astro.ucla.edu/~wright/cosmolog.htm#News]