Is another definition of sum useful?

  • Context: Graduate 
  • Thread starter Thread starter jk22
  • Start date Start date
  • Tags Tags
    Definition Sum
Click For Summary

Discussion Overview

The discussion revolves around the implications of redefining the sum of operators in quantum mechanics, particularly in relation to Bell's theorem and the spectrum of operator sums. Participants explore whether an alternative definition, specifically using the tensor product, could resolve certain contradictions observed in the traditional operator summation.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant suggests that redefining the sum of operators as $$A\otimes 1+1\otimes B$$ resolves the inequality $$\sigma(A+B) \neq \sigma(A) + \sigma(B)$$ into an equality, potentially simplifying the analysis.
  • Another participant cautions that changing definitions can lead to new problems, emphasizing that definitions should not alter the fundamental nature of physical phenomena.
  • A different viewpoint questions whether Bell's theorem can be rephrased in terms of the usual sum of operators, specifically referencing the equation $$1+1+1-1=2\sqrt{2}$$ and the need to clarify the operation of addition between measurement results.
  • A later post expresses confusion regarding discrepancies between measurement results (0, 2, 4) and eigenvalues (0, 2√2), indicating a need for further clarification on the relationship between these quantities.

Areas of Agreement / Disagreement

Participants express differing views on the utility and implications of redefining the sum of operators, with no consensus reached on whether this approach is beneficial or problematic.

Contextual Notes

The discussion highlights potential limitations in the definitions used and the assumptions underlying the mathematical relationships, particularly in the context of quantum mechanics and measurement theory.

jk22
Messages
732
Reaction score
25
Von neumann and bell pointed out that basically the non isomorphic fact that the spectrum $$\sigma(A+B)!=\sigma(A)+\sigma(B)$$ leads to contradictions.

If we but replace the sum by $$A\otimes 1+1\otimes B$$ then the above inequality becomes an equality.
This would make things much easier.

We would get as eigenvalues for chsh integer values for example.
 
Physics news on Phys.org
Note: The inequality sign is \neq to give ##\neq##.

It is always possible to define a problem away - but adopting the definition in general leads to other problems in other places.
In this case, the observation is about something of Nature. You don't get to make Nature something else by changing the definitions of the words used to describe Her.
 
But in our case with the usual sum of operators Bell's theorem could be rephrased as $$1+1+1-1=2\sqrt{2}$$ ? (if we compute the values that are afterwards averaged)

Where we need to find the operation + between measurement results.
 
Last edited:
My last post is confusing, in fact what I mean is that There seem to be a discrepancy between measurement results (0,2,4) and eigenvalues (0,2sqrt 2) ?
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
1K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 15 ·
Replies
15
Views
2K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 16 ·
Replies
16
Views
4K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 69 ·
3
Replies
69
Views
9K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K