Undergrad How do hidden variables supposedly explain radioactive decay?

[BWV]

If individual atoms are indistinguishable from one another, then how can you tell if atom A will experience radioactive decay before identical atom B? ISTM there would have to be some underlying structure beyond electrons and quarks and unique to each atom / particle to be able to do this. This seems like a strong argument for true stochastic behavior of QM systems, but a sizeable minority of real scientists who understand QM still hold out for deterministic rules, so what am I missing?

 

[Nugatory]

There are many random phenomenona that can in principle be explained by a deterministic hidden variable theory; for example we accept the results of a coin toss as random even though with a complete specification of all the variables involved we could calculate the exact trajectory of the coin and how it will land.

Before the discovery of quantum mechanics, it was easy to believe that all randomness could be viewed in this way, not as a fundamental non-determinism in the operation of the universe but rather as a result of our incomplete knowledge of the deterministic conditions at work. When non-determinism appeared in quantum mechanics, at first it seemed natural to make the same assumption that the apparent randomness reflected only our ignorance of some "real" underlying deterministic theory; this thinking was behind the the EPR assertion that QM was incomplete and the famous soundbite about God not playing dice.

A century of failure to find any such theory, and Bell's proof that if we do find such a theory it will be no less offensive to our classical intuition than quantum randomness have taken most of the fun out of this line of thought.

 

[PeterDonis]

QM, as a physical theory that makes predictions about the probabilities of various results of measurements, cannot answer the questions you are asking. Various QM interpretations give different answers to them--further discussion of that should really be done in the QM interpretations forum. However, QM interpretations don't give any way of testing different alternatives, since they all make the same predictions for all experimental results. Unless and until we find a more comprehensive theory to which our current QM is an approximation, we won't be able to do anything more than speculate.

 

[Demystifier]

If individual atoms are indistinguishable from one another, then how can you tell if atom A will experience radioactive decay before identical atom B? ISTM there would have to be some underlying structure beyond electrons and quarks and unique to each atom / particle to be able to do this. This seems like a strong argument for true stochastic behavior of QM systems, but a sizeable minority of real scientists who understand QM still hold out for deterministic rules, so what am I missing?

Your question cannot be answered without talking about quantum interpretations, which is considered appropriate only if the thread gets moved to the appropriate subforum.

 

[BWV]

Then can it be moved to the appropriate location?

 

[PeterDonis]

can it be moved to the appropriate location?

Done. Please note, however, that this changes the thread level to "I", since it's not really possible to discuss QM interpretations at the "B" level (even basic QM without digging into interpretations is hard to discuss at the "B" level).

 

[Demystifier]

If individual atoms are indistinguishable from one another, then how can you tell if atom A will experience radioactive decay before identical atom B? ISTM there would have to be some underlying structure beyond electrons and quarks and unique to each atom / particle to be able to do this. This seems like a strong argument for true stochastic behavior of QM systems, but a sizeable minority of real scientists who understand QM still hold out for deterministic rules, so what am I missing?

The indistinguishability is a property of the wave function. But the Bohmian interpretation (which is the best known hidden variable interpretation) says that particles are more than a wave function, so hidden variables make particles distinguishable. I think it answers your question, but if not feel free to ask for additional clarifications.