Modern Cosmology , Scott Dodelson, Academic Press, San Diego, CA, 2003. $70.00 (440 pp.). ISBN 0-12-219141-2
When I was a graduate student more than 25 years ago, graduate textbooks on cosmology were few and far between. James E. Peebles’s now out-of-print Physical Cosmology (Princeton U. Press, 1971) was not a textbook in the conventional sense but more a set of concise review articles. By far the most useful book was Steven Weinberg’s magnificent Gravitation and Cosmology: Principles and Applications of the General Theory of Relativity (Wiley, 1972). A rich book full of insights, it provided a comprehensive introduction to the literature of the time.
Today’s graduate student is spoiled for choice. Graduate textbooks on cosmology include Peebles’s surprisingly verbose Principles of Physical Cosmology (Princeton U. Press, 1993); John Peacock’s quirky Cosmological Physics (Cambridge U. Press, 1999); Peter Coles and Francesco Lucchin’s Cosmology: The Origin and Evolution of Cosmic Structure (Wiley, 2002); and specialized textbooks on the early universe, such as Edward Kolb and Michael Turner’s The Early Universe (Addison Wesley, 1990) and Andrew Liddle and David Lyth’s more recent Cosmological Inflation and Large-Scale Structure (Cambridge U. Press, 2000).
Scott Dodelson’s Modern Cosmology can now be added to the growing list of cosmology books. The preface opens with a quotation from the “Ethics of the Fathers” found in the Mishnah, a collection of Jewish oral law: “Be patient before reaching a decision; Enable many students to stand on their own; Make a fence around your teaching.” Dodelson’s particular fence is to limit the contents to small-amplitude (that is, linear) perturbations of the homogeneous Friedmann-Robertson-Walker cosmological models. His approach is sensible because linear perturbation theory in that context is relatively simple and well understood.
The material Dodelson offers will not become obsolete quickly and has many important applications, most notably in the analysis of the large-scale distribution of matter in the universe and in the study of the tiny temperature variations in the cosmic microwave background (CMB) radiation, which was mapped to high accuracy last year by the Wilkinson Microwave Anisotropy Probe (WMAP).
What Dodelson provides in the first seven chapters is covered in other cosmology books. The reader has to wait until the final third of the book for significant new material. There, Dodelson offers useful chapters on weak gravitational lensing, polarization of the CMB, and the statistical analysis of cosmological data sets—all important and highly topical areas of research. Overall, the book closely mirrors Dodelson’s own research interests on the CMB and large-scale structure in the universe.
Overlap with other textbooks need not be a major criticism of the book. Dodelson writes well and the mathematical derivations are generally well laid out and easy to follow. Useful sets of exercises appear at the end of each chapter, along with suggestions for further reading, often with amusing commentaries. New graduate students, Dodelson’s intended audience, should find it easy to learn from this book.
Some aspects of the book, however, are less successful. Dodelson states in his preface, “General relativity is an essential tool, so a course in GR would be helpful, but I have tried to introduce the features we will need when we need them.” In my view, that approach doesn’t work very well. For example, chapter 2 contains a single page on manipulating tensorial indexes, which gives the reader no intuitive feel of these operations. Yet within five pages, the Friedmann-Robertson-Walker solutions of the Einstein equations are derived in all their glory. This patchiness extends to the sections of the book on general relativistic perturbation theory. Chapter 4 introduces the conformal Newtonian gauge without any detailed discussion. It offers only an obtuse reference to gauge freedom in electromagnetism. One has to wait until the end of chapter 5 for a brief and incomplete discussion of the conformal gauge.
My strongest criticism is of chapter 6, in which the discussion of inflationary models is far too brief. Inflation is one of the most important ideas in modern cosmology and fits beautifully with the recent CMB results from the WMAP satellite. Yet Dodelson does not even attempt to describe the type of physics that might give rise to inflation.
Would I recommend this book to one of my graduate students? Yes. What it does, it does well. But the book is limited and needs to be supplemented by other material. It often reads like a set of graduate lecture notes and sometimes skirts around technically difficult questions. For these reasons, I doubt whether the book will have a long lifetime, but it does fill a niche for now.
In the meantime, Weinberg is working on a new edition of Gravitation and Cosmology. If the new edition is anywhere near as good as his 1972 original version, then I would bet that a new generation of cosmologists will learn their subject from a particle physicist, just as I did.
