Exploring QM Interpretations: Copenhagen & Blockworld

[Lynch101]

TL;DR Summary

Questions about some of the ideas in the thread Implications of Quantum Foundations on Interpretations of Relativity.

Reading the very interesting thread that @Demystifier started, I was hoping to get a better understanding of certain ideas. I don't think these questions would be suitable for that particular thread.

The first such question pertains to the following exchange between DarMM and Demystifier.

Well a simple example might be Copenhagen and the Blockworld, what you call the spacetime interpretation. In Copenhagen measurement results don't exist prior to the measurement

there is no direct contradiction between blockworld interpretation of relativity and the idea that a measurement result doesn't exist prior to the measurement. One can simply say that the measurement result exists at the spacetime point at which the measurement is performed.

Are there interpretations of QM which require the possibility of more than one outcome in an experiment i.e. where the outcome is not pre-determined?

I was thinking that Copenhagen* was one such interpretation and would therefore not be compatible with the blockworld interpretation of relativity.*or some versions of Copenhagen

 

[dextercioby]

Just to let you know, DarMM has left this community.

 

[Lynch101]

Just to let you know, DarMM has left this community.

Thanks for the heads up!

 

[A. Neumaier]

Just to let you know, DarMM has left this community.

Well, he has a reputation for repeatedly disappearing for some years , only to return later...

 

[Lynch101]

Just to let you know, DarMM has left this community.

Would you happen to know if there interpretations of QM which require the possibility of more than one outcome in an experiment i.e. where the outcome is not pre-determined?

 

[dextercioby]

Would you happen to know if there interpretations of QM which require the possibility of more than one outcome in an experiment i.e. where the outcome is not pre-determined?

I am sorry, I am a fan of the mathematical subleties of quantum mechanics (especially rigged Hilbert spaces), not of interpretations.

 

[Lynch101]

I am sorry, I am a fan of the mathematical subleties of quantum mechanics (especially rigged Hilbert spaces), not of interpretations.

Thanks anyway dextercioby

 

[Lynch101]

Well, he has a reputation for repeatedly disappearing for some years , only to return later...

Would you happen to know if there interpretations of QM which require the possibility of more than one outcome in an experiment i.e. where the outcome is not pre-determined?

 

[A. Neumaier]

Would you happen to know if there interpretations of QM which require the possibility of more than one outcome in an experiment i.e. where the outcome is not pre-determined?

The Copenhagen interpretation and Many worlds have this property. Deterministic foundations like the Thermal Interpretation and Bohmian mechanics don't have it. Statistical interpretations are silent about it.

 

[PeterDonis]

The Copenhagen interpretation and Many worlds have this property.

But they have it in two very different ways. In Copenhagen, only one outcome actually occurs, but the outcome is not determined by the prior state; it is randomly chosen from among the possible outcomes. So more than one outcome is possible before the result is known, but only one outcome actually occurs.

In the MWI, the evolution is entirely deterministic, and this deterministic evolution leads to all possible outcomes occurring. So more than one outcome is not only possible, but actual.

 

[Lynch101]

The Copenhagen interpretation and Many worlds have this property.

In Copenhagen, only one outcome actually occurs, but the outcome is not determined by the prior state; it is randomly chosen from among the possible outcomes. So more than one outcome is possible before the result is known, but only one outcome actually occurs.

Thanks. I was thinking that it was a feature of Copenhagen that more than one outcome must be possible, but I wasn't sure if it was an absolute necessity; to the extent that it would make it incompatible with the spactime/blockworld formulation of relativity.

 

[A. Neumaier]

Thanks. I was thinking that it was a feature of Copenhagen that more than one outcome must be possible, but I wasn't sure if it was an absolute necessity; to the extent that it would make it incompatible with the spactime/blockworld formulation of relativity.

Almost by definition, a blockworld makes sense only in a deterministic setting.

 

[WernerQH]

Almost by definition, a blockworld makes sense only in a deterministic setting.

I don't understand this. Why would a blockworld view imply determinism? Perhaps it's just a matter of terminology -- I like to think of statistical ensembles of possible blockworlds. (Perhaps more appropriately called "patches of spacetime").

 

[A. Neumaier]

I don't understand this. Why would a blockworld view imply determinism? Perhaps it's just a matter of terminology -- I like to think of statistical ensembles of possible blockworlds. (Perhaps more appropriately called "patches of spacetime").

Given an ensemble of blockworlds, the dynamics in each particular blockworld is deterministic. Once in a blockworld there is no further choice. The other blockworlds are completely irrelevant for observers in a particular one.

This is also the reason why the many worlds interpretation is an empty interpretation - it just says that anything can happen in the actual world we live in.

 

[Lynch101]

Almost by definition, a blockworld makes sense only in a deterministic setting.

Yes, this is what I was thinking. Demystifier put forward an argument [in the thread from which this thread is spun] suggesting that the blockworld doesn't necessarily require or imply determinism, but it would still be incompatible with any interpretation that requires the possibility of more than one outcome in the experiment.

 

[WernerQH]

Given an ensemble of blockworlds, the dynamics in each particular blockworld is deterministic.

Why couldn't there be some stochastic dynamics?

 

[A. Neumaier]

Why couldn't there be some stochastic dynamics?

Because by definition, each blockworld fixes everything as a function of spacetime. The only conceivable stochastic dynamics could be in another dimension where one can move between blockworlds. But this extra dimension would have nothing to do with time. The latter is intrinsic to each single blockworld.

 

[WernerQH]

Because by definition, each blockworld fixes everything as a function of spacetime.

Oh, if it's by definition, then I should choose a different name. :-)
Thanks!