Johnson, Matthew C. and Kamionkowski, Marc (2008) Dynamical and gravitational instability of an oscillating-field dark energy and dark matter. Physical Review D, 78 (6). Art. No. 063010. ISSN 0556-2821 http://resolver.caltech.edu/CaltechAUTHORS:JOHprd08
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Coherent oscillations of a scalar field can mimic the behavior of a perfect fluid with an equation-of-state parameter determined by the properties of the potential, possibly driving accelerated expansion in the early Universe (inflation) and/or in the Universe today (dark energy) or behaving as dark matter. We consider the growth of inhomogeneities in such a field, mapping the problem to that of two coupled anharmonic oscillators. We provide a simple physical argument that oscillating fields with a negative equation-of-state parameter possess a large-scale dynamical instability to growth of inhomogeneities. This instability renders these models unsuitable for explaining cosmic acceleration. We then consider the gravitational instability of oscillating fields in potentials that are close to, but not precisely, harmonic. We use these results to show that if axions make up the dark matter, then the small-scale cutoff in the matter power spectrum is around 10^-15M⊕.
|Additional Information:||©2008 The American Physical Society. (Received 22 May 2008; published 18 September 2008) We thank D. Cohen for discussions of Floquet theory, L. Kofman for suggesting some useful papers, and C. Hirata for discussions and suggestions. This work was supported by the DOE DE-FG03-92-ER40701 and the Gordon and Betty Moore Foundation.|
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|Deposited On:||20 Sep 2008 01:14|
|Last Modified:||26 Dec 2012 10:18|
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