I The lore on complex probabilities

[arivero]

I think that the lore on the need of having probability interference in quantum mechanics and then a complex probability originates in Feynman interpretation of space-time paths, whose probability is weighed with a complex exponential that approaches a dirac delta.

But I can not pinpoint a concrete source of this lore; perhaps it even predated the path integral. Any guesses?

 

[anuttarasammyak]

AFAIK Dirac mentioned it in 32. The Action Principle, The Principles of Quantum Mechanics.

 

[arivero]

Going to check, thanks. It makes sense because Feynman claims to have got is insight from Dirac, I think from some work on contact transformations. But also [I believe to remember that he told...] that he was unable to agree with Dirac on the significance.

 

[arivero]

I see, this is the third edition, that already uses Dirac notation:

Is it the same in the 1932 edition?

 

[dextercioby]

1930 you mean. It was the 1st edition, second came in 1935, third in 1947, and fourth and final in 1958. I don't have access to any of thr first two editions. Very rare in libraries.