Isocurvature forecast in the anthropic axion window

Journal Article · Mon Jun 01 04:00:00 EDT 2009 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2009/06/022· OSTI ID:22273152

Hamann, J. ^[1]; Hannestad, S. ^[2]; Raffelt, G. G. ^[3]; Wong, Y. Y.Y., ^[4]

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1. LAPTh, Université de Savoie, CNRS, BP 110, F-74941 Annecy-le-Vieux Cedex (France)
2. Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)
3. Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, D-80805 München (Germany)
4. Theory Division, Physics Department, CERN, CH-1211 Genève 23 (Switzerland)

We explore the cosmological sensitivity to the amplitude of isocurvature fluctuations that would be caused by axions in the ''anthropic window'' where the axion decay constant f{sub a} >> 10{sup 12} GeV and the initial misalignment angle Θ{sub i} << 1. In a minimal ΛCDM cosmology extended with subdominant scale-invariant isocurvature fluctuations, existing data constrain the isocurvature fraction to α < 0.09 at 95% C.L. If no signal shows up, Planck can improve this constraint to 0.042 while an ultimate CMB probe limited only by cosmic variance in both temperature and E-polarisation can reach 0.017, about a factor of five better than the current limit. In the parameter space of f{sub a} and H{sub I} (Hubble parameter during inflation) we identify a small region where axion detection remains within the reach of realistic cosmological probes.

• OSTI ID: 22273152
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 06 Vol. 2009; ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AMPLITUDES
AXIONS
COSMOLOGICAL CONSTANT
COSMOLOGY
FLUCTUATIONS
LIMITING VALUES
POLARIZATION
PROBES
RELICT RADIATION
SENSITIVITY