What do we really know about Dark Energy?

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Ruth Durrer
In this paper I discuss what we truly know about dark energy. I shall argue that up to date our single indication for the existence of dark energy comes from distance measurements and their relation to redshift. Supernovae, CMB anisotropies and observations of baryon acoustic oscillations, they all simply tell us that the observed distance to a given redshift is larger than the one expected from a Friedmann Lemaitre universe with matter only and the locally measured Hubble parameter…..
…….. Read more:
In this work I have pointed out that all present claims about the existence of dark energy have not measured ΩΛ or even less ΩDE and w directly, but just the distance redshift relation DL(z).
They then have inferred the existence of dark energy by assuming the form (3) for this relation, which holds in a FL universe. Even though many of you (especially the observers, I guess) may regard this point as trivial, I find it important to be aware of it before one is ready to postulate unobserved scalar fields with most unusual properties, or violations of General Relativity on large scales.
I have not discussed the many possible pitfalls of the observations, which weaken any one observation, but my confidence relies on the fact that independent observations with different systematics find the same result. I hope they are not too strongly influenced by ’sociology’, i.e.: if your finding disagrees with the results of others it must be wrong and therefore you do not publish it, however, if it agrees well it must be right and therefore you do not have to investigate every possible systematics which would increase your error bars and make your result less competitive”.
The beauty of research in cosmology is that data come in fast and there is justified hope that the question whether relation (3) holds for the real Universe,
will be answered in the not very far future.

Written by physicsgg

October 9, 2011 at 11:40 am


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