B Why Does Cosmic Growth End and Why Is Our Era Unique?

[wolram]

Why do we live in such a privileged time?

arXiv:1810.10547 [pdf, ps, other]
The End of Cosmic Growth
Eric V. Linder, David Polarski
Comments: 5 pages, 6 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The growth of large scale structure is a battle between gravitational attraction and cosmic acceleration. We investigate the future behavior of cosmic growth under both general relativity (GR) and modified gravity during prolonged acceleration, deriving analytic asymptotic behaviors and showing that gravity generally loses and growth ends. We also note the `why now' problem is equally striking when viewed in terms of the shut down of growth. For many models inside GR the gravitational growth index γ also shows today as a unique time between constant behavior in the past and a higher asymptotic value in the future. Interestingly, while f(R) models depart in this respect dramatically from GR today and in the recent past, their growth indices are identical in the asymptotic future and past.

 

[George Jones]

I think that the title of this thread is misleading the article

arXiv:1810.10547 [pdf, ps, other]
The End of Cosmic Growth
Eric V. Linder, David Polarski
Comments: 5 pages, 6 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

is not about the of expansion of the universe, it is about the end of growth of structures in the universe. Very roughly, the proper distance between structures is accelerating, not slowing down, but growth rate of the structures themselves will slow down (in many models).

 

[Grinkle]

Why do we live in such a privileged time?

There may be a more satisfying answer than the anthropic principle, but that certainly applies. You definitely won't catch fish if your cast doesn't land in water.