lunes, 12 de octubre de 2015

Heisenberg y los observables

Heisenberg y los observables

Generalmente es reconocido el hecho de que el papel publicado en julio de 1925 por Werner Heisenberg es el que di fin a la “Teora Cuntica Vieja”, y que con la exposicin de su Mecnica Matricial se di entrada a la Mecnica Cuntica tal como se conoce y se practica en la actualidad.

Heisenber mismo, en su famoso articulo fundacional de la nueva mecánica cuántica, resaltaria el hecho de que “it is well known that the formal rules which are used in quantum theory for calculating observable quantities such as the energy of the hydrogen atom may be seriously criticzised on the grounds that they contain, as basic element, relationships between quantities that are apparently unobservable in principle, e.g., position and period of revolution of electron... Experience however shows that only the hydrogen atom and its Stark effect are amenable to treatment by these formal rules of quantum teory”.
Heisenberg también critica el principio de correspondencia: “It has become the practice to characterize this failure of the quantum-theoretical rules as a deviation from classical mechanics, since the rules themselves were essentially derived from classical mechanics.”
Y en concordancia con Husserl:
On doit s'accommoder du fait que ce n'est qu' travers le processus de connaissance lui-mme que se dcide ce qu'on doit entendre par "connaissance". [...] Toute formulation dans le langage est toujours, non seulement une saisie de la ralit, mais aussi une manire de la mettre en forme et de l'idaliser [...] La connaissance n'est sans doute en dernire instance rien d'autre que l'agencement non pas l'agencement de quelque chose qui serait dj disponible en tant qu'objet de notre conscience ou de notre perception, mais plutt l'agencement de quelque chose qui ne devient un veritable contenu de conscience ou un processus perceptif qu' travers cet agencement meme (Whm, 363-364)
"Philosophie. Le manuscrit de 1942"
Heisenberg, W. Philosophie. Le manuscrit de 1942. Introduction et traduction par C. Chevalley (490 p.). Editions du Seuil, 1998. Premire dition en allemand : Ordnung der Wirklichkeit, 1989. Seconde dition francaise : Arla, 2003, 2010 (173 p.)

da el paso fundamental que destraba el callejon sin salida a que habia llegado la mecanica cuantica.
In this situation it seems sensible to discard all hope of observing hitherto unobservable quantites, such as the position and period of electron, and to concede that the partial agreement of the quantum rules with experience is more or less fortuitous. Instead it seems more reasonable to try to establish a theoretical quantum mechanics, analogous to classical mechanics, but in which only relations between observable quantities occur.”
Dando a luz la mecánica matricial. Y abriendo una nueva dimension para la fisica.

Quantum-theoretical re-interpretation of kinematic and mechanical relations. W.Heisenberg

As hitherto defined, quantum mechanics enables the radiation
emitted by the atom, the energy values of the stationary states, and other
parameters characteristic for the stationary states to be treated. The theory
hence complies with the experimental data contained in atomic spectra. In all those cases, however, where a visual description is required of a transient event, e.g. When interpreting Wilson photographs, the formalism of the theory does not seem to allow an adequate representation of the experimental state of affairs. At this point Schrödinger’s wave mechanics, menawhile developed on the basis of the de Broglie’s theses, came to the assistance of quantum mechanics.
Tal como Heisenberg lo considera, el cambio de la mecánica clásica a la mecánica cuántica fue así:
In classical physics the aim of research was to investigate objective processes occurring in space and time, and to discover the laws governing their progress from the initial conditions. In classical physics a problem was considered solved when a particular phenomenon had been proved to occur objectively in space and time, and it have been shown to obey the general rules of classical physics as formulated by differential equations.
The manner in which the knowledge of each process had been acquired, what observations may possibly have led to its experimental determination, was completely immaterial, and it was also immaterial for the consequences of the classical theory, which possible observations were to verify the predicitions of the theory. In the quantum theory, however, the situation is completely different. The very fact that the formalism of quantum mechanics cannot be interpreted as visual description of a phenomenom occurring in space and time shows that quantum mechanics is in no way concerned with the objective determination of space - time phenomena. On the contrary, the formalism of quantum mechanics should be used in such a way that the probability for the outcome of a further experiment may be concluded from the determination of an experimental situation in an atomic system, providing that the system is subject to no perturbations other than those necessitated by performing the two experiments.

Nobel Lecture 1939 Heisenberg.

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