In What Sense Is the Early Universe Fine-Tuned?

In Barry Loewer, Brad Weslake & Eric B. Winsberg (eds.), The Probability Map of the Universe: Essays on David Albert’s _Time and Chance_. Cambridge MA: Harvard University Press (2023)
  Copy   BIBTEX

Abstract

It is commonplace in discussions of modern cosmology to assert that the early universe began in a special state. Conventionally, cosmologists characterize this fine-tuning in terms of the horizon and flatness problems. I argue that the fine-tuning is real, but these problems aren't the best way to think about it: causal disconnection of separated regions isn't the real problem, and flatness isn't a problem at all. Fine-tuning is better understood in terms of a measure on the space of trajectories: given reasonable conditions in the late universe, the fraction of cosmological histories that were smooth at early times is incredibly tiny. This discussion helps clarify what is required by a complete theory of cosmological initial conditions.

Author's Profile

Sean M. Carroll
Johns Hopkins University

Analytics

Added to PP
2016-06-16

Downloads
1,299 (#10,974)

6 months
204 (#12,382)

Historical graph of downloads since first upload
This graph includes both downloads from PhilArchive and clicks on external links on PhilPapers.
How can I increase my downloads?