11697 8 archive 1 disk0/00/01/16/97 2008-09-20 01:14:47 2008-09-20 01:14:47 2008-09-20 01:14:47 article show 0 Johnson Matthew C. Johnson-M-C Kamionkowski Marc Kamionkowski-M pub cls public ©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. 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⊕. 2008-09-15 published Physical Review D 78 6 American Physical Society Art. No. 063010 CaltechAUTHORS:JOHprd08 TRUE 1550-7998 http://resolver.caltech.edu/CaltechAUTHORS:JOHprd08 http://dx.doi.org/10.1103/PhysRevD.78.063010 doi http://link.aps.org/abstract/PRD/v78/e063010 pub 1. S. Perlmutter et al. (Supernova Cosmology Project Collaboration), Astrophys. J. 517, 565 (1999); A. G. Riess et al. (Supernova Search Team Collaboration), Astron. J. 116, 1009 (1998). 2. B. Ratra and P. J. E. Peebles, Phys. Rev. D 37, 3406 (1988); C. Wetterich, Astron. Astrophys. 301, 321 (1995); K. Coble, S. Dodelson, and J. A. Frieman, Phys. Rev. D 55, 1851 (1997); M. S. Turner and M. J. White, Phys. Rev. D 56, R4439 (1997); R. R. Caldwell, R. Dave, and P. J. Steinhardt, Phys. Rev. Lett. 80, 1582 (1998). 3. L. A. Boyle, R. R. Caldwell, and M. Kamionkowski, Phys. Lett. B 545, 17 (2002). 4. J. A. Gu and W. Y. Hwang, Phys. Lett. B 517, 1 (2001). 5. M. S. Turner, Phys. Rev. D 28, 1243 (1983). 6. T. Damour and V. F. Mukhanov, Phys. Rev. Lett. 80, 3440 (1998). 7. A. R. Liddle and A. Mazumdar, Phys. Rev. D 58, 083508 (1998). 8. J. w. Lee, S. Koh, C. Park, S. J. Sin, and C. H. Lee, Phys. Rev. D 61, 027301 (1999). 9. V. H. Cardenas and G. Palma, Phys. Rev. D 61, 027302 (1999). 10. M. Sami, Gravitation Cosmol. 8, 309 (2003). 11. V. Sahni, M. Sami, and T. Souradeep, Phys. Rev. D 65, 023518 (2001). 12. A. R. Liddle and R. J. Scherrer, Phys. Rev. D 59, 023509 (1998). 13. M. Sami, N. Dadhich, and T. Shiromizu, Phys. Lett. B 568, 118 (2003). 14. L. Perivolaropoulos, Phys. Rev. D 67, 123516 (2003). 15. V. Sahni and L. M. Wang, Phys. Rev. D 62, 103517 (2000). 16. E. Masso, F. Rota, and G. Zsembinszki, Phys. Rev. D 72, 084007 (2005). 17. J. a. Gu, arXiv:0711.3606. 18. S. D. H. Hsu, Phys. Lett. B 567, 9 (2003). 19. S. Dutta and R. J. Scherrer, arXiv:0805.0763. 20. M. Sami and T. Padmanabhan, Phys. Rev. D 67, 083509 (2003); 67, 109901 (2003). 21. S. Tsujikawa, Phys. Rev. D 61, 083516 (2000). 22. A. Taruya, Phys. Rev. D 59, 103505 (1999). 23. S. Kasuya, M. Kawasaki, and F. Takahashi, Phys. Lett. B 559, 99 (2003). 24. S. Kasuya, Phys. Lett. B 515, 121 (2001). 25. M. Khlopov, B. A. Malomed, and I. B. Zeldovich, Mon. Not. R. Astron. Soc. 215, 575 (1985). 26. W. Hu, R. Barkana, and A. Gruzinov, Phys. Rev. Lett. 85, 1158 (2000). 27. A. Kusenko and M. E. Shaposhnikov, Phys. Lett. B 418, 46 (1998); K. Enqvist and J. McDonald, Nucl. Phys. B38, 321 (1999); S. Kasuya, Phys. Lett. B 515, 121 (2001). 28. J. Frank, A. King, and D. Raine, Accretion Power in Astrophysics (Cambridge University Press, Cambridge, 2002). 29. W. Magnus and S. Winkler, Hill's Equation (Interscience Publishers, New York, 1966). 30. G. N. Felder, L. Kofman, and A. D. Linde, Phys. Rev. D 64, 123517 (2001). 31. M. S. Turner, Phys. Rep. 197, 67 (1990); G. G. Raffelt, Phys. Rep. 198, 1 (1990); L. J. Rosenberg and K. A. van Bibber, Phys. Rep. 325, 1 (2000); S. J. Asztalos, L. J. Rosenberg, K. van Bibber, P. Sikivie, and K. Zioutas, Annu. Rev. Nucl. Part. Sci. 56, 293 (2006). 32. J. Diemand, B. Moore, and J. Stadel, Nature (London) 433, 389 (2005). 33. M. Kamionkowski and S. M. Koushiappas, Phys. Rev. D 77, 103509 (2008). 34. S. Profumo, K. Sigurdson, and M. Kamionkowski, Phys. Rev. Lett. 97, 031301 (2006). 35. P. B. Greene, L. Kofman, and A. A. Starobinsky, Nucl. Phys. B43, 423 (1999). 36. Y. Shtanov, J. H. Traschen, and R. H. Brandenberger, Phys. Rev. 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