Axion as a cold dark matter candidate: analysis to third order perturbation for classical axion
- Center for Large Telescope, Korea Astronomy and Space Science Institute, 776 Daedeok Dae-ro, Yuseong-gu, Daejeon 34055 (Korea, Republic of)
- Department of Astronomy and Atmospheric Sciences, Kyungpook National University, 80 Daehak-ro, Sankeok-dong, Buk-gu, Daegu 41566 (Korea, Republic of)
- Division of Science Education and Institute of Fusion Science, Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju 54896 (Korea, Republic of)
We investigate aspects of axion as a coherently oscillating massive classical scalar field by analyzing third order perturbations in Einstein's gravity in the axion-comoving gauge. The axion fluid has its characteristic pressure term leading to an axion Jeans scale which is cosmologically negligible for a canonical axion mass. Our classically derived axion pressure term in Einstein's gravity is identical to the one derived in the non-relativistic quantum mechanical context in the literature. We present the general relativistic continuity and Euler equations for an axion fluid valid up to third order perturbation. Equations for axion are exactly the same as that of a zero-pressure fluid in Einstein's gravity except for an axion pressure term in the Euler equation. Our analysis includes the cosmological constant.
- OSTI ID:
- 22525142
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Vol. 2015, Issue 12; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
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