Angel "Java" Lopez en Blog

8 de Diciembre, 2020


Publicado el 8 de Diciembre, 2020, 13:11

Sigo leyendo a Arnold Sommerfeld (1868-1951). Esta vez su "Wave-Mechanics" que mencioné en Arnold Sommerfeld sobre Atomos y Espectro como continuación de su clásico "Atom Structure and Line Spectra". Esa continuación sólo apareció con las nuevas ediciones: la primera fue publicada en 1919 donde todavía no se había desarrollado la mecánica cuántica. Es interesante leer:

I have called this volume a "wave-mechanical" supplement, becauSe for practical manipulation Schrödinger's methods are obviously superior to the specifics,lly U quantum-mechanical" methods.. On the other hand, however, I have left no doubt :hat the general ideas that have led Heisenberg to, enunciate quantum-mecbanics . are also indispensable for the elaboration of wave-mechanics. The original standpoint of Schrödinger, that transitions are to occur only between co-existing states, is clearly too narrow and does not accurately fit the facts. I have therefore taken over into wave-mechanics the equal treatment of states and transitions, -as is done by Heisenberg from the very beginning, - in particular in deriving the frequency-condition and the rules of polarisation and, intensity in section 5, chapter I. This, of course, denotes that I am renouncing the more definite wave-kinematic objective, set up by Schrödinger and de Broglie, and am sacrificing pictorial representatiqn to formalism. In wave-mechanics the electron still remains a point-charge ultimately, and the light- quantum a point-like centre of energy. But the dualism between the light-quantum and the light-wave extends into the corpuscular region; beside the electron-corpuscle we have the electron-wave with all the accumulative experimental evidence to confirm it.

Digo, interesante que haya preferido a la descripción de Schrödinger pero reconociendo las limitaciones que tiene (muy asociada a electrones ligados) con respecto a la de Heisenberg. Habría que esperar a Dirac para ver la equivalencia de ambos desarrollos.

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 8 de Diciembre, 2020, 10:47

Sigo leyendo el clásico "Atom Structure and Spectra Lines" de Arnold Sommerfeld. En las primeras páginas hay una descripción de cómo el electromagnetismo se fue desarrollando en el siglo XIX, titulado "1.1 Retrospect of the Development of Electrodynamics":

In the first half of the nineteenth century Electrodynamics consisted of a series of disconnected elementary laws. Formed analogously to Newton's Laws of Gravitation, they asserted the existence of direct action at a distance, which, starting from the seat of an electric charge or of a magnetism and leaping over the invervening space was supposed to act at the seat of a second electric or magnetic charge.

Es interesante que se comenzó con acción a distancia, siguiendo las ideas de Newton, criticadas varias veces en los siglos desde su aparición. También es de destacar la ausencia de un concepto como el elctrón, y no se sabía si había carga eléctrica Y carga magnética.

Opposed to this there arose in the second half of the nineteenth century a view which followed the course of the continuously extended electromagnetic field from point to point and momento to momento: it was called the "Field Theory" in contradiction to the "Theory of Action at a Distance." It was propounded by Faraday, worked out by Maxwall, and completed by Heinrich Hertz. According to this view the electromagnetic field is represented by the course, in space and time, of the electric and magnetic lines of forcé. Maxwell's teach us how electric and magnetic lines of forcé are linked with one another, how magnetic changes at any point of the field call up electrical forces, and how electric currents are surrounded by magnetic forces. The invervening médium, even if non-conducting, is supposed to have a certain transparency (permeability) and receptivity (dialectric capacity) towards magnetic and electric lines of forcé; hence at every point of space it influences the distribution of the electromagnetic field according to its constituion at that point.

Interesante: el concepto de campo es sugerido por Faraday, alguien sin educación formal en física. Tal vez una mente así, fresca, sin influencia "newtoniana", pudo concenbir esa idea, aunque también hay que ver que puede surgir simplemente de los experimentos. Notablemente, el concepto de campo no apareció en gravitación, posiblemente debido a la poca intensidad relativa a la experiencia humana de esa fuerza.

En próximo post, seguiré compartiendo y comentado esta interesante retrospectiva de Sommerfeld.

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia