Llego al final de esta conferencia de Dirac. Luego de observar algunos problemas, menciona la renormalización de los valores del electrón:
A feature of the calculations leading to the Lamb shift and anomalous magnetic moment should be noted. One finds that the parameters m and e denoting the mass and charge of the electron in the starting equations are not the same as the observed values for these quantities. If we keep the symbols m and e to denote the observed values, we have to replace the m and e in the starting equations by m + dm and e + be, where dm and be are small corrections which can be calculated. This procedure is known as renormalization.
Dirac ve que este "truco" funciona porque es un cambio global:
Such a change in the starting equations is permitted. We can take any starting equations we like, and then develop the theory by making deductions from them. You might think that the work of the theoretical physicist is easy if he can make any starting assumptions he likes, but the difficulty arises because he needs the same starting assumptions for all the applications of the theory. This very strongly restricts his freedom. Renormalization is permitted because it is a simple change which can be applied universally whenever one has charged particles interacting with the electromagnetic field.
Yo no sabía que hay otros problemas asociados con la autoenergía del fotón, también:
There is a serious difficulty still remaining in quantum electrodynamics, connected with the self-energy of the photon. It will have to be dealt with by some further change in the starting equations, of a more complicated kind than renormalization.
Finalmente, el objetivo final según Dirac:
The ultimate goal is to obtain suitable starting equations from which the whole of atomic physics can be deduced. We are still far from it. One way of proceeding towards it is first to perfect the theory of low-energy physics, which is quantum electrodynamics, and then try to extend it to higher and higher energies. However, the present quantum electrodynamics does not conform to the high standard of mathematical beauty that one would expect for a fundamental physical theory, and leads one to suspect that a drastic alteration of basic ideas is still needed.
Fue una larga serie post, con varios puntos que tengo que estudiar y comentar con mejor detalle.
Angel "Java" Lopez