Axions, Inflation and the Anthropic Principle
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Tue, 11/05/2010 12:00 |
Katherine Mack (Cambridge) |
Quantum Field Theory Seminar  |
L3 |
| The QCD axion is the leading solution to the strong-CP problem, a dark matter candidate, and a possible result of string theory compactifications. However, for axions produced before inflation, high symmetry-breaking scales (such as those favored in string-theoretic axion models) are ruled out by cosmological constraints unless both the axion misalignment angle and the inflationary Hubble scale are extremely fine-tuned. I will discuss how attempting to accommodate a high-scale axion in inflationary cosmology leads to a fine-tuning problem that is worse than the strong-CP problem the axion was originally invented to solve, and how this problem is exacerbated when additional axion-like fields from string theory are taken into account. This problem remains unresolved by anthropic selection arguments commonly applied to the high-scale axion scenario. | |||