The relationship between classical and quantum theory is of central importance to the philosophy of physics, and any interpretation of quantum mechanics has to clarify it. Our discussion of this relationship is partly historical and conceptual, but mostly technical and mathematically rigorous, including over 500 references. For example, we sketch how certain intuitive ideas of the founders of quantum theory have fared in the light of current mathematical knowledge. One such idea that has certainly stood the test of time is (...) Heisenberg's `quantum-theoretical Umdeutung (reinterpretation) of classical observables', which lies at the basis of quantization theory. Similarly, Bohr's correspondence principle (in somewhat revised form) and Schroedinger's wave packets (or coherent states) continue to be of great importance in understanding classical behaviour from quantum mechanics. On the other hand, no consensus has been reached on the Copenhagen Interpretation, but in view of the parodies of it one typically finds in the literature we describe it in detail. On the assumption that quantum mechanics is universal and complete, we discuss three ways in which classical physics has so far been believed to emerge from quantum physics, namely in the limit h -> 0 of small Planck's constant (in a finite system), in the limit N goes to infinity of a large system with $N$ degrees of freedom (at fixed h), and through decoherence and consistent histories. The first limit is closely related to modern quantization theory and microlocal analysis, whereas the second involves methods of C*-algebras and the concepts of superselection sectors and macroscopic observables. In these limits, the classical world does not emerge as a sharply defined objective reality, but rather as an approximate appearance relative to certain ``classical" states and observables. Decoherence subsequently clarifies the role of such states, in that they are ``einselected", i.e. robust against coupling to the environment. Furthermore, the nature of classical observables is elucidated by the fact that they typically define (approximately) consistent sets of histories. This combination of ideas and techniques does not quite resolve the measurement problem, but it does make the point that classicality results from the elimination of certain states and observables from quantum theory. Thus the classical world is not created by observation (as Heisenberg once claimed), but rather by the lack of it. (shrink)

Příspěvek se zaměřuje na zavádějící příběh o tzv. kodaňské interpretaci kvantové mechaniky, již jako údajně nerozpornou či jednotnou vytvořili a sdíleli na základě tzv. kodaňského ducha kvantové teorie její tvůrci v roce 1927. Článek bude vycházet z role, kterou v tomto příběhu sehráli především N. Bohr a W. Heisenberg. První část příspěvku seznamuje s variacemi toho, co se v literatuře považuje za kodaňskou interpretaci. Druhá část odhaluje, že zatímco kvantová mechanika vznikla ve dvacátých letech 20. století, kodaňská interpretace je veskrze (...) problematickým a především Heisenbergovým produktem z let padesátých. Jednou z hlavních motivací, kvůli níž vystoupil s tzv. kodaňskou interpretací, byla obrana vůči množícím se kritikám obhájců kvantové teorie. Jelikož mezi členy tzv. kodaňské školy nepanovala žádná jednotná či nerozporná interpretace kvantové mechaniky, zaměřuje se poslední část příspěvku na několik vybraných rozdílů hlavně mezi Bohrovým a Heisenbergovým výkladem kvantové teorie. (shrink)

According to the standard view, the so-called ‘Copenhagen interpretation’ of quantum mechanics originated in discussions between Bohr and Heisenberg in 1927, and was defended by Bohr in his classic debate with Einstein. Yet recent scholarship has shown Bohr’s views were never widely accepted, let alone properly understood, by his contemporaries, many of whom held divergent views of the ‘Copenhagen orthodoxy’. This paper examines how the ‘myth of the Copenhagen interpretation’ was constructed by situating it in the context of Soviet Marxist (...) critique of quantum mechanics in the 1950s and the response by physicists such as Heisenberg and Rosenfeld. (shrink)

The London and Bauer monograph occupies a central place in the debate concerning the quantum measurement problem. Gavroglu has previously noted the influence of Husserlian phenomenology on London's scientific work. However, he has not explored the full extent of this influence in the monograph itself. I begin this paper by outlining the important role played by the monograph in the debate. In effect, it acted as a kind of 'lens' through which the standard, or Copenhagen, 'solution' to the measurement problem (...) came to be perceived and, as such, it was robustly criticized, most notably by Putnam and Shimony. I then spell out the Husserlian understanding of consciousness in order to illuminate the traces of this understanding within the London and Bauer text. This, in turn, yields a new perspective on this 'solution' to the measurement problem, one that I believe has not been articulated before and, furthermore, which is immune to the criticisms of Putnam and Shimony. (shrink)