D O C . 7 7 E S S E N C E O F Q U A N T U M M E C H A N I C S 8 3 In my opinion, one can eliminate this objection only in this way: one does not describe the process only in terms of the Schrödinger wave, but at the same time, one must localize the particle during its propagation. I think that Mr. de Broglie is correct in investigating along these lines. If one makes use only of Schrödinger waves, the interpretation II of implies in my view that it is a contradiction with the principle of relativity. I would like also to briefly mention two arguments that seem to me to plead against concept II. That concept is essentially connected to a polydimensional rep- resentation (configuration space), since only that representation makes possible the interpretation of as in concept II. Now, it seems to me that there are objections in principle against such a polydimensional representation.[7] In such a representa- tion, indeed, two configurations of a system, which are distinguished only by a per- mutation of two particles of the same species, are denoted by two different points (within configuration space), which disagrees with new results in statistics.[8] Fur- thermore, the particular property of forces, of acting only at small spatial distances, is less naturally expressed in configuration space than in a space of three or four dimensions. … Photons Mr. Kramers.— Mr. Brillouin has explained to us during the discussion of Mr. de Broglie’s report how the pressure of the light behaves in the case of interference and that one must presume an auxiliary tension. But how does the pressure of the light behave in the case where it is so weak that there is only one photon in the re- gion of interference? And how does one obtain the auxiliary tensor in that case? Mr. de Broglie.— The demonstration of the existence of these tensions cannot be done unless one considers a cloud of photons. Mr. Kramers.— And if there is only one photon, how can one account for the sudden change in the amount of movement that the reflecting object undergoes? Mr. Brillouin.— No theory actually gives the answer to Mr. Kramer’s question. Mr. Kramers.— Without doubt, shouldn’t a complicated mechanism be imag- ined that cannot be deduced from the electromagnetic wave theory? Mr. de Broglie.— The dualist representation by corpuscles and associated waves does not constitute a definitive picture of the phenomena. It does not allow for fore- seeing the pressures exerted on the different points of a mirror during reflection of a single photon. It only gives the average value of the pressure at the time of the reflection of a cloud of photons. Mr. Kramers.— What advantage do you see in giving a precise value to the speed v of the photons? [p. 256]  2  2 [p. 265] [p. 266]