TY  - JOUR
N1  - ©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.
ID  - caltechauthors11697
UR  - http://resolver.caltech.edu/CaltechAUTHORS:JOHprd08
IS  - 6
A1  - Johnson, Matthew C.
A1  - Kamionkowski, Marc
Y1  - 2008/09/15/
N2  - 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?.
PB  - American Physical Society
JF  - Physical Review D
VL  - 78
SN  - 1550-7998
TI  - Dynamical and gravitational instability of an oscillating-field dark energy and dark matter
SP  - 11697
AV  - public
EP  - /RIS
ER  -