Dear Editor,

Thank you very much for asking me to referee this paper. It is very interesting and it almost certainly deserves publication. The level of detail in this work and the performance gain that has been achieved by the authors is impressive.

However, as much as I like the work by these authors, I am unable to referee the article for you. Together with almost 10000 other scientists, I’ve signed a pledge to not publish, referee or do editorial work for any article that is published by Elsevier (http://thecostofknowledge.com/). I strongly believe that scientific publications should be freely available to everyone. Elsevier is the antithesis to that statement and I don’t want to support their business model. The company makes an annual profit of over one billion dollars and has reported a profit margin of 36%. These exorbitantly high figures are due to disproportionately expensive library subscriptions charged to universities and research institutions which are forced to buy journal subscriptions in large bundles. Elsevier itself is adding almost no value in the peer-review process. The work is done by researchers and referees which are mainly paid with public funds.

Fortunately, scientific publishing is evolving rapidly. For example, I’ve already been able to read this paper a month ago because the authors posted it on the arXiv preprint server which is a free, donation supported service run by a non-profit organization.

For these reasons, I am sorry to say that I cannot assist you in this case. I hope that you will find another person willing to referee this paper. If the authors decide to withdraw their paper and submit it to another journal, I’m more than happy to be the referee.

Kind regards,
Hanno Rein

PS: I’m afraid that the ’30 days full access to Scopus, the world’s largest abstract and citation database of research information and quality internet sources’ that you’ve offered me in your e-mail is not going to change my mind.

Hanno Rein, John C. B. Papaloizou

Many small moonlets, creating propeller structures, have been found in Saturn’s rings by the Cassini spacecraft. We study the dynamical evolution of such 20-50m sized bodies which are embedded in Saturn’s rings. We estimate the importance of various interaction processes with the ring particles on the moonlet’s eccentricity and semi-major axis analytically. For low ring surface densities, the main effects on the evolution of the eccentricity and the semi-major axis are found to be due to collisions and the gravitational interaction with particles in the vicinity of the moonlet. For large surface densities, the gravitational interaction with self-gravitating wakes becomes important.
We also perform realistic three dimensional, collisional N-body simulations with up to a quarter of a million particles. A new set of pseudo shear periodic boundary conditions is used which reduces the computational costs by an order of magnitude compared to previous studies. Our analytic estimates are confirmed to within a factor of two.

On short timescales the evolution is always dominated by stochastic effects caused by collisions and gravitational interaction with self-gravitating ring particles. These result in a random walk of the moonlet’s semi-major axis. The eccentricity of the moonlet quickly reaches an equilibrium value due to collisional damping. The average change in semi-major axis of the moonlet after 100 orbital periods is 10-100m. This translates to an offset in the azimuthal direction of several hundred kilometres. We expect that such a shift is easily observable.

Preprint

http://arxiv.org/abs/1006.1643

Movies

Simulation EQ40050DT:

Update: A new feature “SkyView” lets you see the position of all exoplanets on a sky chart.

My third paper appeared on the arXiv today. It discusses the so called super-particle approximation that many people use but might not be valid in any situation.