## Friday, 14 March 2008

### New Scientist and dark energy without dark energy

Some time ago I have decided to subscribe to New Scientist. My reactions are, on the average, rather mixed. Half o f the printed pages are taken by job postings for UK (which are rather uninteresting for me. And the general tabloid style, which I have already ridiculed here is a bit too tabloid.

But there is a positive side of the `hunt for the NEWS' approach, which, in summary more than compensated the shortcomings. It is exactly the tabloid style hunt for the man bites dog sensational news that allows to find scientific research that is off the beaten path.

The reason for this mention is the reference to works of David Wiltshire, especially his efforts to build alternative to the $\Lambda CDM$ cosmology model. Ever since the discovery of the acceleration of the expansion of the Universe, I have felt that the acceptance of the Dark Energy/Dark Matter Universe, despite the 120 orders of magnitude discrepancy with the basic quantum `explanation', was a bit too fast.
My own experiences with solid state physics are that if anyone proposes an explanation that is off the data by, a single order of magnitude, it is `suspect', two orders make it useless. But hundred and twenty orders of magnitude? Yet the astrophysics community has accepted the 70%/25%/5% explanation so easily, without real understanding about what these 95% of the Universe are made of. Carroll's Preposterous Universe offers a good label for this quick understanding.

For these reasons I am grateful to the New Scientist for pointing out the work of Wiltshire. His papers, on Dark Energy without Dark Energy and Cosmic clocks, cosmic variance and cosmic averages, available on the WEB, are rather difficult in their mathematical part, but they are also very pedagogical.
In the words of the author:
An overview is presented of a recently proposed "radically conservative" solution to the problem of dark energy in cosmology. The proposal yields a model universe which appears to be quantitatively viable, in terms of its fit to supernovae luminosity distances, the angular scale of the sound horizon in the cosmic microwave background (CMB) anisotropy spectrum, and the baryon acoustic oscillation scale. It may simultaneously resolve key anomalies relating to primordial lithium abundances, CMB ellipticity, the expansion age of the universe and the Hubble bubble feature. The model uses only general relativity, and matter obeying the strong energy condition, but revisits operational issues in interpreting average measurements in our presently inhomogeneous universe, from first principles. The present overview examines both the foundational issues concerning the definition of gravitational energy in a dynamically expanding space, the quantitative predictions of the new model and its best-fit cosmological parameters, and the prospects for an era of new observational tests in cosmology.

While the calculations are rather intricate (too intricate for this amateur), the background physics and assumptions used are physical common sense and with much closer links to reality (such as observations of inhomogeneity of the Universe) that the Dark Energy models.

Why is then Wiltshire's work not the hot topic of astrophysics conferences?