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In What Sense Is the Early Universe Fine-Tuned?

Carroll, Sean M. (2014) In What Sense Is the Early Universe Fine-Tuned? . (Submitted)

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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.

Item Type:Report or Paper (Discussion Paper)
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Carroll, Sean M.0000-0002-4226-5758
Additional Information:Imported from arXiv. It is a pleasure to thank David Albert for inspiration and conversations over the years, Barry Loewer for his patience, Shelly Goldstein for useful discussions, my collaborators Heywood Tam and Grant Remmen for their invaluable insights, and Tim Maudlin for the interactions that proximately inspired this paper. This research is funded in part by DOE grant DESC0011632, and by the Gordon and Betty Moore Foundation through Grant 776 to the Caltech Moore Center for Theoretical Cosmology and Physics.
Group:Walter Burke Institute for Theoretical Physics, Caltech Theory, Moore Center for Theoretical Cosmology and Physics
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Department of Energy (DOE)DESC0011632
Gordon and Betty Moore Foundation776
Walter Burke Institute for Theoretical Physics at CaltechUNSPECIFIED
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Record Number:CaltechAUTHORS:20140716-105154654
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:47263
Deposited By: Joy Painter
Deposited On:16 Jul 2014 23:38
Last Modified:02 Jun 2023 00:20

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