To be honest, this book is a must have for anybody out there who wants to work in the new so-called precision cosmology (CMB temperature and polarization anisotropy, large scale galaxy redshift survey, weak lensing etc.). I am actually not working in cosmology, but I have been spending quite some time teaching myself cosmology, and I can say that this book has become gold mine when I tried to understand Boltzmann equation in the context of cosmology.

The Boltzmann equation relates the time evolution of thermodynamic distribution function of a species to collisions or interactions between species. Some treatments of Boltzmann equation can be found in elementary statistical physics or solid state physics. The species under consideration are electrons, phonons, photons, or atoms.

In the context of cosmology, things are become more complicated due to three things:

1) General relativistic approach. We must take into account the perturbed metric and cosmic expansion.

2) There are exotic species such as dark matter and neutrinos besides the CMB photons, electrons, and baryons.

3) The interactions are not only electromagnetic.

The books is a bit concise, but with a careful reading it really helps. It begins with three chapters introducing essentials of general relativity, kinetic theory, and general relativistic Boltzmann equation. Then it introduces the canonical example of one particle species with self-interaction. The general Lee-Weinberg problem of stable, neutral particle-antiparticle species are treated in two chapters with great details. Unstable particles comes next. The final two chapters deal with recombination and helium production.

A treatment with similar spirit can be found in some chapters of Scott Dodelson's Modern Cosmology (Academic Press, 2003, ISBN 0122191412) but in less detail. Dodelson himself suggested this book for further reading. Dodelson worked with the author of this book when the book was still in the writing phase, and the author did mention his name in the preface.

Table of Contents 1. Tools: relativity 2. Tools: cosmodynamics 3. Tools: kinetic theory 4. The canonical example 5. The generalized Lee-Weinberg problem: background 6. The generalized Lee-Weinberg problem: examples 7. Unstable particles 8. The recombination regime 9. Cosmological helium production Five appendices without titles.

Too bad this book is out of print now. Try your local library, inter-library loan, or buy it used. Get it, you will need it during your whole cosmology career to understand Boltzmann equation in cosmology.