- #36
Borean
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It seems you don't agree with each other.Pio2001 said:Hello,
Here is the current state of affairs to my knowledge.
Let's use the definitions given by Borean : indeterminacy means that there are some events whose cause we don't know, and acausality that there are some events that have no cause at all.
It's been common practice to name "hidden variable" an unknown cause that would give birth to the values that quantum mechanics doesn't predict in the measurment process. So if hidden variables doesn't exist, then the universe is acausal.
In 1964, Bell proves that quantum mechanics is in contradiction with local hidden variables (hidden variables whose effect travels slower or at the speed of light).
In 1967, Kochen and Specker prove that no hidden variables can be carried by the measured system and bear all prédictions about their possible measured properties. If hidden variable exist, local or not, they depend at least party, on the measurment setup. They are contextual.
In 1969, Bell's theorem was generalized by Clauser, Horne, Shimony and Holt to contextual hidden variables.
In 1982, Alain Aspect's experiment shows that quantum mechanics predictions in Bell and CHSH theorems are fullfilled. Therefore if the universe is causal, then it is non-local.
The Kochen-Specker theorem have been tested too. The results of a recent experiment by Roos, Blatt et al have just been published in Nature. It confirms the inexistence of non-contextual hidden variables with great accuracy.
Another recent experiment by Gröblacher et al ruled out a whole class of non-local hidden variable interpretations : http://www.arxiv.org/PS_cache/arxiv/pdf/0704/0704.2529v1.pdf
I'm not sure which class exactly, but it seems to me that they are interpretations without entanglement.
So we're left with some philosophiocal problems. Experiments give us the choice between
-Leaving out causality : some events occur without any cause.
-Leaving out locality : the cause of an event can lie in its future.
-Leaving out realism : there is no reality. There is just information gathered by observers.
The Copenhagen interpretation makes both the first and third choices, as well as Rovelli's relational interpretation.
Cramer's transactional interpretation makes the second choice. As did Böhm-De Broglie's pilot wave interpretation (but they didn't know it before Bell's theorem).
Everett many-world's interpretations are usually not developped enough to get a precise position in this choice. JesseM, in this forum, used to describe an extension of Everett's interpretation that would get rid of these three problems ( but introducing the existence of many worlds of course) : https://www.physicsforums.com/showthread.php?t=206291#11
I can only guess, then, that there is no consensus?
To the causalists who said that causality is preserved in quantum theory: how do you answer the above post?