Von Neumann's uniqueness theorem (CCR representations)

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Discussion Overview

The discussion revolves around von Neumann's uniqueness theorem related to CCR (canonical commutation relations) representations, focusing on the proof of certain properties of operators and their kernels. Participants explore the original sources and seek clarification on specific mathematical terms and derivations.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant requests the proof of a statement regarding projectors in the context of von Neumann's work.
  • Another participant notes that the only explicit proof is found in von Neumann's original article.
  • A participant seeks clarification on the translation of the German word "Kern" and its modern mathematical equivalent, suggesting it may refer to an integral kernel.
  • There is a discussion about how von Neumann calculates the "Kern" of operators and the relationship between them, with a participant asking how to derive formulas for specific operators from these kernels.
  • Some participants mention that later accounts of von Neumann's work are less detailed and do not provide explicit calculations.

Areas of Agreement / Disagreement

Participants generally agree that von Neumann's original article contains the necessary proofs, but there is no consensus on the specifics of the calculations or the terminology used, indicating ongoing uncertainty and exploration.

Contextual Notes

Limitations include potential ambiguity in the term "Kern" and its translation, as well as the reliance on von Neumann's original calculations, which may not be fully detailed in later interpretations.

Who May Find This Useful

This discussion may be useful for those interested in mathematical physics, operator theory, and the historical context of quantum mechanics, particularly in relation to von Neumann's contributions.

Heidi
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Hi Pfs,
Please read this paper (equation 4):
https://ncatlab.org/nla b/files/RedeiCCRRepUniqueness.pdf
It is written: Surprise! P is a projector (has to be proved)...
where can we read the proof?
 
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thanks Demystifier.
 
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Thank you for bringing it up. I will check in von Neumann's original proof or some other source.
 
The only explicit proof is in von Neumann's original article.
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thanks, it's a good opportunity to revise my German a bit (I studied English and German when in high school)
 
Tell me if this is correct:
To prove that A and AS(u,v)A only differ by a numerical factor, Von Neumann
calculates the "Kern" of A then of SA and then of ASA. As these "kerns" differ by a m
multiplicative constant k, then ASA = k A.
I would like to know how to translate the german word "Kern" in modern math english. Is it really integral kernel? or characteristic functional?
How to derive his forulas for A and SA?
 
Yes, an integral kernel is the modern term. As for the calculations themselves are all made by von Neumann. Later accounts (Putnam for example) are telegraphic, no explicit calculations
 
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  • #10
In the paper Von Neumann considers three operators containing integrals. For each of them , he gives its kernel .
How to retrieve A , SA and ASA from these kernels?
 

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