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a Recent paper establishes under solid grounds anisotropy in the expansion acceleration rate in the universe. My question is very simple:

can this anomaly be explained entirely in terms of a cosmological constant?

I suspect that by adjusting the $\alpha$ scale factor to depend not only on time but also on a unit direction it seems that one could explain the above anisotropy without appealing to any exotic field (other than a cosmological constant) but then you only do not know why the asymmetry in the boundary condition (early universe) exists in the first place

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This paper is somewhat interesting, but overall I am really not convinced. The paper barely mentions the CMB, which is probably a more reliable indication of universal isotropy than supernova redshift. (If there was a preferred expansion direction, you would expect some sort of strange pattern in CMB redshift) –  Benjamin Horowitz Sep 7 '11 at 18:26

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I highly doubt quintessence is the only possibility, as long as the framework of models you are talking about is completely general.

I believe you could always create such anisotropies by introducing spatial variations in the Hubble rate (http://arxiv.org/abs/0709.2044), f.e. by invoking the cosmic bubble hypothesis, which assumes that we live inside an underdense region. As soon as we are not located in ther centre of the bubble, anisotropy should arise.

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