The material on variational methods presented in this book was developed over the past 10-15 years by many people working in the field of nuclear reactor physics, and the author's debt to these people will be evident from the text. For the most part, this material has been published in technical journals and reports, and one of the purposes of writing this book was to collect and codify it. The selection of what to include was based upon an attempt to cover all of the relevant ideas without unnecessary redundancy, but, of course, was biased by the author's conception of work in reactor physics on variational methods. Extensive references provide a guide to work not explicitly developed in the text.
This book is intended as a reference for engineers and scientists. The mathematical level of the material should be accessible to anyone who has had the standard undergraduate courses in differential equations and matrix algebra and who is familiar with the concept of an operator and its manipulations, although some knowledge of the calculus of variations would be helpful.