Axions, inflation and the anthropic principle

Journal Article · Fri Jul 01 04:00:00 EDT 2011 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2011/07/021· OSTI ID:22277780

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, symmetry-breaking scales of f{sub a}∼>10{sup 12} GeV (which are favored in string-theoretic axion models) are ruled out by cosmological constraints unless both the axion misalignment angle θ{sub 0} and the inflationary Hubble scale H{sub I} are extremely fine-tuned. We show that attempting to accommodate a high-f{sub a} 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. We also show that this problem remains unresolved by anthropic selection arguments commonly applied to the high-f{sub a} axion scenario.

• OSTI ID: 22277780
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 07 Vol. 2011; ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AXIONS
COMPACTIFICATION
COSMOLOGY
CP INVARIANCE
GEV RANGE
INFLATIONARY UNIVERSE
INFLATONS
MATHEMATICAL SOLUTIONS
NONLUMINOUS MATTER
QUANTUM CHROMODYNAMICS
STRING MODELS
STRING THEORY
SYMMETRY BREAKING