Inflation Unloaded

TL;DR

The paper discusses how future accelerated expansion limits observable inflationary periods, suggesting current CMB data may be the furthest we can ever observe in the universe's history.

Contribution

It reviews the implications of eternal acceleration on the observability of inflationary epochs and the potential limits on cosmological information accessible to us.

Findings

Future acceleration can obscure earlier inflation signatures.

Event horizons limit the observable number of efolds of inflation.

Current CMB data may be the ultimate observable record of the universe's history.

Abstract

I present a brief review of astro-ph/0406099, which argues that there is a limit on the number of efolds of inflation which are observable in a universe which undergoes an eternally accelerated expansion in the future. Such an acceleration can arise from an equation of state p = w \rho, with w < -1/3, and it implies the existence of event horizons. In some respects the future acceleration acts as a second period of inflation, and "initial perturbations" (including signatures of the first inflationary period) are inflated away or thermalize with the ambient Hawking radiation. Thus the current CMB data may be looking as far back in the history of the universe as will ever be possible even in principle, making our era a most opportune time to study cosmology.