We have just returned from a talk by the Bethe colloquium. Erik Verlinde from the university of Amsterdam spoke about “Dark Matter, Dark Energy and the Emergence of Gravity ”.
In his talk, he showed that his approach can not only reproduce the MONDian behavior of the different kinds of galaxies. He even gave an explanation on why the centers of galaxy clusters deviate from the baryonic Tully-Fisher relation by a factor of four. The reason, he says, lies in the distribution of matter. Very roughly, galaxies can be approximated by a point mass if we look at their outskirts only. In galaxy clusters, however, the matter is more evenly distributed. Assuming a spatially constant matter density, he can even motivate the amount of the deviation
All in all, his results look very promising. After the talk, Pavel and I discussed with him for about an hour, explaining some of the failures of the LCDM model, but mostly asking about details and implications of his approach. He explained that his intention is to understand gravity by starting from scratch. So not only change and modify the formula used so far, but basing our understanding of gravity on a more fundamental basis. To do so, he looks at the observational evidence unbiased. We agreed that this is not always easy because especially cosmological results are usually analyzed and expressed in a model-dependent form. He does not aim at reproducing MOND, which even its adherents usually describe rather as a phenomenological effect than a new fundamental law. But his model naturally contains MONDian behavior, it seems to explain/give a reason for MOND's free parameter (the acceleration a0) and he also showed that his approach can predict the ratio of baryonic to (phantom) dark matter correctly: 4% to 22.5%.
What he told was impressive and looks like it could be a major step forward in our understanding of gravity and the universe. Unfortunately, we have to wait some more until he will publish a paper on this topic. But there is good reason to look forward to it.
By Pavel Kroupa and Marcel Pawlowski (28.06.2012): "Discussing Gravity with Erik Verlinde" on SciLogs. See the overview of topics in The Dark Matter Crisis.