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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

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 (, 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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