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En estos días vuelvo a leer a Max Jammer, a quien mencioné en:
Uhlenbeck, Goudsmit y el spin del electron
Max Jammer y el Formalismo de la Mecánica Cuántica
Estoy leyendo su excelente libro "The Conceptual Development of Quantum Mechanics", edición 1966. Leo:
It is the purpose of this study to trace the conceptual development of quantum mechanics from its inception to its formulation as a full-fledged theory of atomic physics, from its status as a rather doubtful ad hoc hypothesis to that of an imposing intellectual structure of great beauty.
Trata de la mecánica cuántica no relativista de una cantidad finite de grados de libertad, que abarca los primeros desarrollos exitoso, digamos, hasta parte de la tercera década del siglo XX. Las primeras preguntas que nos aparecen son: ¿qué es el desarrollo conceptual? ¿es necesario en este tema?.
All the great theories in the history of physics—from Aristotelian mechanics and its medieval elaborations, through Newtonian dynamics with its Lagrangian or Hamiltonian modifications, to Maxwellian electrodynamics and* Einsteinian relativity—have been subjected repeatedly to historico-critical investigations, and their conceptual foundations have been thoroughly analyzed. But no comprehensive scholarly study of the conceptual development of quantum mechanics has heretofore appeared. The popular or semiscientific publications available hardly skim the surface of the subject. And the few, though important, essays on the topic written by the originators of the theory themselves are mostly confined to a particular aspect or to the defense of a specific philosophical position. The publication of a comprehensive and coherent analysis of the conceptual development of quantum mechanics, the only consistent theory of atomic processes, and hence a foundation of modern science, seems therefore to fill an important lacuna in the literature on the history and philosophy of physics.
Primero, es un libro sobre el desarrollo de las ideas. No es un libro de texto para APRENDER mecánica cuántica, sino para entender cómo se fue desarrollando. Por otro lado, no es un libro solamente con el desarrollo histórico: habrá ocasiones donde Jammer se concentra en el desarrollo de una idea, sin importar que ese desarrollo se superponga en años históricos con otro desarrollo de otra idea.
Such a study, however, should not be regarded as an end in itself. Never before has a theory been treated in so many excellent texts within so short a period of time. Since every additional text, as is natural in a developing branch of science, attempts to construct the theory on the basis of an ever more concise logical structure, the traditional texts presenting the material in the order of its historical development are gradually losing ground. Students, it is rightfully claimed, may be saved much trouble "if they are not led through all the historical pitfalls, and instead acquainted from the very beginning with concepts, such as the spin, that cannot be grasped except by quantum mechanical means." [cita 1] Admittedly, a good working knowledge, even a high standard of efficiency and competence in applying the theory to physical problems may be obtained by this method of instruction. But as long as it is true that "however far the phenomena transcend the scope of classical physical explanation, the account of all evidence must be expressed in classical terms," [cita 2] a profound comprehension of quantum mechanics requires more than a study of the subject in its shortest possible logical formulation. "It is impossible to understand the methods of modern quantum mechanics without a knowledge of the way in which the theory has been developing." [cita 3] Indeed, some knowledge of the dramatic struggle of ideas that preceded the formation of quantum conceptions and of the intricate ways of reasoning that led to the generally accepted formulation of the theory is indispensable for a profound comprehension of its physical significance, for an intelligent appreciation of its philosophical implications, and even for an enlightened understanding of its logical structure. Duhem's statement "faire l'histoire d'un principe physique, c'est en meme temps en faire l'analyse logique" is particularly meaningful for the science of quantum mechanics.
Hoy aprendemos física clásica, digamos la mecánica newtoniana, sin estudiar ni su desarrollo histórico ni conceptual (¿cómo surgió el concepto de energía? ¿y el de momento angular?). Pero en cuántica, y en especial en mecánica cuántica, pasa que si bien se puede aprenderla sin necesitar de la historia o el desarrollo, sus conceptos, operaciones y formalismos son tan extraños a la intuición que para realmente comprenderla, atraparla en su esencia, puede que no haya otro camino que el emprendido por Jammer: el desarrollo de las ideas, para explicar fenómenos que no cuajan en el marco "clásico". Es cierto que hay muy buenos libros para comenzar a entender la mecánica cuántica (y luego la física cuántica) desde algunos principios, sin tener que seguir todo el desarrollo ni histórico ni conceptual. Pero es como que se pierde algo. Un excelente libro que recuerdo ahora, que sigue un desarrollo histórico, más que conceptual, es el Física Cuántica, de Eisberg y Resnick, que era un clásico en mis días de estudiante universitario.
La cita 1 es F.A.Kaempffer, Concepts in Quantum Mechanics. La cita 2 es de Niels Bohr, "Discussion with Einstein on epistemological problems in atomic physics". La cita 3 es A.March, Quantum Mechanics of Particles and Wave Fields.
Seguiré citando y comentando algunos temas de este libro. Es interesante, por ejemplo, cómo plantea que los desarrollos de Jordan y de Dirac, a partir de 1925, son como un contrapunto: mientras el primero se concentra en teorías de campo, el segundo prefirió una vision desde el modelo de partículas.
Nos leemos!
Angel "Java" Lopez
http://www.ajlopez.com
https://twitter.com/ajlopez
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