Copenhagen - What qualifies as "measurement" and "observer"?

[bhobba]

OK, perhaps it is just semantics.

That's all much of this is IMHO.

Thanks
Bill

 

[atyy]

That's all much of this is IMHO.

I'm not sure. If you agree with my analogy with GRW/CSL versus Copenhagen Continuous Measurement, then in the former we can have a state of the universe including the observer (ie. quantum mechanics without observers), while in the latter there is no meaning to the state of the universe.

Also, GRW and CSL and Bohmian Mechanics, as I understand, do eventually lead to deviations from quantum mechanics, which I think can be in principle tested (maybe even in practice as discussed by the link http://arxiv.org/abs/1410.0270 posted by Jimster41).

 

[bhobba]

It is an intriguing open question whether the linearity of quantum mechanics extends into the macroscopic domain.

The key point of assuming its a proper mixture is there is some process that makes it a proper mixture - that linearity breaks down is one way to explain it - but not the only one.

Thanks
Bill

 

[atyy]

The key point of assuming its a proper mixture is there is some process that makes it a proper mixture - that linearity breaks down is one way to explain it - but not the only one.

The idea is that so far assuming one world, if one is to seriously solve the factorization problem as BM, GRW and CSL try to do, then the linearity does break down. This is why the factorization problem is stressed by some for the emergence of classical reality without a privileged status for observers.

 

[Jimster41]

I'm not sure. If you agree with my analogy with GRW/CSL versus Copenhagen Continuous Measurement, then in the former we can have a state of the universe including the observer (ie. quantum mechanics without observers), while in the latter there is no meaning to the state of the universe.

Also, GRW and CSL and Bohmian Mechanics, as I understand, do eventually lead to deviations from quantum mechanics, which I think can be in principle tested (maybe even in practice as discussed by the link http://arxiv.org/abs/1410.0270 posted by Jimster41).

Just want to mention that @bhobba (as well as others) pointed me to that paper.