Niels Bohr and complementarity. An introduction.
Complementarity is a central concept in the Copenhagen interpretation of quantum mechanics. Its advent and the development of its meaning is illustrated in course of the formulation and consolidation of quantum mechanics from 1900 to 1962. A main purpose of the book is to promote a true understanding of Niels Bohr's thinking and writings which are sometimes tentative and give rise to confusion. The lifelong debates of Bohr with Albert Einstein are valuable sources to achieve this goal. Chapter 1 is an introductory overview of the entire time. Chapter 2 concerns the year 1913 when Bohr published his postulates on stationary orbits of the electron in the planetary atomic model and the emission or absorption of light quanta by quantum jumps. The correspondence of Bohr with Rutherford, who found the paper too long, is the frame story to mediate Bohr's epistemological thoughts about his postulates. The chapter closes with Einstein's word: ``this is the highest musicality in the sphere of thought.'' Chapter 3 considers the transition from the ``old quantum theory'' to the matrix and wave mechanics. Bohr was aware of these new approaches, the duality of wave and particle and the uncertainty relation when he created his first version of complementarity. Bohr's correspondence principle as well as his view on the relationship between mathematics and physics are described. Chapter 4 is the first one devoted to completely complementarity. The author distills the version proposed in the Como lecture (1927) also from sources which appeared later. Relations to discontinuity and irrationality as well as to space-time coordination and causality are looked on. Influenced by Einstein, Bohr changed to another approach to complementarity even before the Como lecture was published. As described in Chapter 5 complementarity is now based on Heisenberg's uncertainty relation, e.g., position-momentum coordination, called reciprocity. In Chapter 6, Bohr's view on the double slit experiments in the light of the latter version of complementarity is considered. To that end the double slit experiment is described to some extend. It is subject of the Bohr-Einstein debate in the Como conference where the dissent whether quantum mechanics is a complete description of nature came up. Chapter 7 is about quantum field theory. The results of the collaboration of Bohr with Léon Rosenfeld on the measurability of field quantities are considered in relation to the development of quantum field theory based on relativistic wave equations from the beginning up to the introduction of strings and branes. The EPR-paper and Bohr's reply are described and broadly discussed in Chapter 8. How much discussions with Einstein have influenced Bohr's thinking is the contend of the closing section of this chapter. Bohr's ultimate resulting view on quantum theory is discussed in Chapter 9. Bohr's interpretation of the double slit experiment where the locality restriction at the diaphragma causes momentum uncertainty demonstrated by the pattern on the screen, quantum measurements, and particle wave complementarity are displayed. The epistemological views of Bohr and Einstein are compared in the final Chapter 10, ``The unity of knowledge.'' It reviews the time 1954 --1962, when Bohr mediated his picture of the world in several invited talks. Harmonies of thought and knowledge related to mathematics, physics, and philosophy bring together Einstein and Bohr. This book, obviously, is the result of thorough studies of the literature from and about both N. Bohr and A. Einstein and shows up instructively their merits in the development and interpretation of quantum theory.
changes in the meaning of complementarity
scientific article; zbMATH DE number 6054197