Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2010-01-26
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
27 pages, 5 figures, accepted for publication in JCAP
Scientific paper
We revisit ghost dark matter, the possibility that ghost condensation may serve as an alternative to dark matter. In particular, we investigate the Friedmann-Robertson-Walker (FRW) background evolution and the large-scale structure (LSS) in the $\Lambda$GDM universe, i.e. a late-time universe dominated by a cosmological constant and ghost dark matter. The FRW background of the $\Lambda$GDM universe is indistinguishable from that of the standard $\Lambda$CDM universe if $M\gtrsim 1 {\rm eV}$, where $M$ is the scale of spontaneous Lorentz breaking. From the LSS we find a stronger bound: $M\gtrsim 10 {\rm eV}$. For smaller $M$, ghost dark matter would have non-negligible sound speed after the matter-radiation equality, and thus the matter power spectrum would significantly differ from observation. These bounds are compatible with the phenomenological upper bound $M\lesssim 100 {\rm GeV}$ known in the literature.
Furukawa Tomonori
Ichiki Kiyotomo
Mukohyama Shinji
Sugiyama Naoshi
Yokoyama Shuichiro
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