Timeline for Dirac's remark that inspired Feynman when formulating path integral
Current License: CC BY-SA 3.0
6 events
| when toggle format | what | by | license | comment | |
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| Jan 5, 2017 at 21:08 | comment | added | gradStudent | canonical transformations are sometimes called contact transformations, you can read more about this on Goldstein's first edition of classical mechanics. | |
| May 24, 2016 at 4:04 | comment | added | Luboš Motl | On the other hand, the matrix elements - probability amplitudes - are continuous, different from 0 and 1, and basically nonzero for any pair of initial and final state. That's due to the uncertainty principle and this general form of the matrix elements is why Dirac talks about "transformations" in QM - it obviously means unitary transformations but it generalizes the delta-function-based classical contact ones. See motls.blogspot.com/2016/03/… for my text that was trying to convey the same idea, 2nd part. | |
| May 24, 2016 at 4:00 | comment | added | Luboš Motl | I haven't heard it, either, but I have used the same thing in explaining the difference between class physics and QM - without reading this Dirac text. "Transformation" means the transformation of the phase space associated with the time evolution, in this case. The adjective "contact" means that the probability density that the point $(x,p)$ at one moment turns to $(x',p')$ at another moment is proportional to a (Dirac) delta-function - it's only nonzero if one evolves it in the right way. The word "contact" generally does refer to the delta-function, like in "contact interactions". | |
| May 23, 2016 at 20:45 | comment | added | asmaier | Do you happen to know what Dirac means with the term "contact transformations" when he writes in the beginning of the paper: "Lagrangian theory is closely connected with the theory of contact transformations" ? I have never heard the term "contact transformations" anywhere. | |
| Aug 11, 2015 at 7:58 | vote | accept | M. Zeng | ||
| Sep 6, 2014 at 9:15 | history | answered | Luboš Motl | CC BY-SA 3.0 |