By Gösta Ekspong (ed.)
World Scientific
Hardback: £45
E-book: £34
Perhaps every reader of CERN Courier has heard about the Klein–Gordon equation, the Klein–Nishina (Compton effect) cross-section, the Klein paradox and the Kaluza–Klein compactified five-dimensional unified theory of gravity, electricity and magnetism. However, few will know about the scientist, Oskar Klein (1894–1977), the pre-eminent and visionary Swedish theoretical physicist from Stockholm whose work continues to influence us to this day.
This book is needed. The reason is described eloquently in the contribution by Alan Guth, whose words I paraphrase: how many recognize Oskar as the first name of “this” Klein? Compare here (by birth year, within 10 years): Niels B (1885), Hermann W (1885), Erwin S (1887), Satyendra N B (1894), Wolfgang P (1900), Enrico F (1901), Werner H (1901), Paul A M D (1902), Eugene W (1902), Robert O (1904). Thanks to this book, Oskar K (1894) will take his place on this short list.
Part of the book collects together all of the Oskar Klein Memorial Lectures given since the series began at Stockholm University in 1988, through to 1999, by many well-known theoreticians, from Chen Ning Yang to Gerard ’t Hooft. Some of these lectures relate to Klein because he often happened to “be there” at the beginning of a new field in physics. For example, in early 1948, Klein recognized immediately, following the disambiguation of the pion and muon, that muon decay and common beta decay can be described by the same four-fermion interaction (see the contribution by T D Lee).
The other part of the book – a third of the 450 pages – is a biographical collection about Klein and his pivotal scientific articles (about a fifth of the volume), all presented in English, although Klein published in Danish, French, English, German and Swedish, as a check of the titles in his publication list reveals. Having Klein’s important work all in one place can lead to interesting insights: for me, finding that 24 December 1928 was a special birthday.
On this day, just eight weeks after the Klein–Nishina paper on the interaction of radiation with electrons, the paper on the Klein paradox reached the editors of Zeitschrift für Physics. Klein concludes: “…(the) difficulty of the relativistic quantum mechanics emphasized by Dirac can appear already in purely mechanical problems where no radiation processes are involved.” The yet-to-be-recognized and discovered antiparticle – the positron – was the “difficulty”, allowing for both radiative and field-instigated pair production (the “paradox”), when vacuum instability is inherent in a prescribed external field configuration.
The Klein-paradox result resurfaced soon in the work by Werner Heisenberg and Hans Euler, and Julian Schwinger on the vacuum properties of QED. Today, as we head towards the centenary of the Klein paradox, pair production in strong fields is being addressed as a priority within the large community interested in ultra-intense laser pulses.
Oskar Klein was always a colleague I wished I could meet, and finally, I have. Thank you, Gösta Ekspong, for this introduction to my new-found hero. While at first my profound personal interest in this book arose from curiosity originating from many years of working out the consequences of the Klein paradox in heavy-ion collisions, I now see how Klein can serve as a role model. This is the book to own for anyone interested in seeing further by “standing on the shoulders of giants”.
