Surprise, and Pride

Earlier this week, when I had a cursory look at my mailbox at the institute, I was a bit surprised: Usually, it contains only boring information leaflets or updates of phone lists, but this time, there was a big white envelope waiting to be picked up. I was even more surprised when I recognized the sender: Peter Hoyng, a researcher at SRON, the Netherlands Institute for Space Research. I had completely forgotten about him, and for sure, I had not expected that he would, indeed, send me what was in the envelope: a copy of his book, Relativistic Astrophysics and Cosmology - A Primer.



The story had begun in November 2004, when I got an email form someone I had never heard before working at a Dutch research institute I had never heard before. Peter Hoyng told me that he was preparing a textbook on astrophysics and cosmology, condensing into a book the course he has been teaching at the University of Utrecht since several years. He was looking for an illustration of a heavy ion collision that he would like to use in the part on the early universe where the transition from the primordial quark gluon plasma to a hadron gas is discussed. By chance, he had found a snapshot from a simulation of a lead-lead collision at the CERN-SPS in an online talk I had prepared for my PhD advisor a year before. Now, he was interested in a more detailed explanation of the figure, and asked for the permission to use it in his book.

Of course, I was extremely pleased by this request. I provided him with the explanation and a colour version of the figure file, and asked him to tell me when the book will be in print. The next time I heard from him was half a year later, last July, when he contacted me again. He told me about delays in the publishing procedure because of a change of the publisher, and asked me for a black-and-white version of the figure, following the request of the new publisher. I was happy to help him, and completely forgot the whole story - until this week, when I found his book, together with a short note, in my mailbox.

Obviously, there was one more change of the publishing house, since now, colour is used again for the illustrations. The book is very neatly produced, as a part of the Astronomy and Astrophysics Library at Springer. It starts with a motivation for the need of general relativity in astrophysics, introduces the geometry of Riemann spaces and general relativity, and goes on with the Schwarzschild metric, compact stars, and black holes. Two chapters discuss gravitational waves and Fermi-Walker transport (including a discussion of Gravity Probe B). The remaining chapters are devoted to cosmology: the Robertson-Walker metric, the evolution of the universe, observations, the early universe, and inflation. You can download the detailed table of contents on the publishers website of the title.

So far I have only had a cursory look a the book, so this is not a review. But from what I have seen, it looks very interesting and worth reading. I especially appreciate the discussion of interferometric gravitational wave detectors, and Gravity Probe B. Moreover, I am happy to see the onion-like diagrams of light paths in the expanding universe, which you may know from Ned Wrights web site. I have seen these types of diagrams for the first time in a paper by Ellis and Rothman in the American Journal of Physics. I found them extremely useful to develop some kind of visual understanding of the expanding universe, and I wonder how any textbook about cosmology can be without them.

All this, of course, was not the first thing I looked up in the book. I searched the index for quark-gluon plasma, and on page 241, I found my illustration:



It shows a snapshot from a simulation of a collision of two lead nuclei immediately after an off-center impact with an energy of 17.4 GeV per nucleon pair (corresponding to the CERN-SPS), as calculated with the code I have used in my thesis. Unaffected so-called spectator nucleons are white, while deconfined quarks and antiquarks are represented as coloured spheres. There are no gluons in this model - the effect of glue is all subsumed in a linear, confining potential, which is used to describe the interaction between quarks. It comes out of this simple model is that quarks quickly team up in colour-neutral quark-antiquark or three-quark configurations, which are mapped to mesons and baryons, respectively. For better visibility, the figure is stretched in the beam direction by the gamma factor to undo the Lorentz contraction of the colliding nuclei. The gamma factor at this collision energy is of order 10, and the spatial configuration of the collding system in the centre-of-momentum frame is already quite pancake-like...

I guess I will have to write in much more detail about my simulations of the quark-gluon plasma, and this exciting topic in general. I will do so some time... But for now, I am just proud to see this figure of mine reproduced in a textbook.

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TAGS: SCIENCE, PHYSICS, BOOKS