Particle annihilation -- Is it instantaneous?

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During particle annhilation the rest mass of the particle pair gets converted into momentum with zero time component ie. light. As the pair is colliding do their rest masses decrease and get converted to momentum as a function of distance? Or do they instantaneous annihilate in a discrete interval?
 

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  • #2
Nugatory
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All quantum mechanical interactions are black boxes. There is moment when we have the pre-interaction state, there is a later moment when we have the post-interaction state, but the theory says nothing about what happens in between.
 
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Demystifier
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The answer to the question depends on the interpretation. The answer by @Nugatory is correct from the standard minimal point of view.
 
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All quantum mechanical interactions are black boxes. There is moment when we have the pre-interaction state, there is a later moment when we have the post-interaction state, but the theory says nothing about what happens in between.

This is very important. QM says nothing about what happens in between. Even some well respected physicists like Sabine Hossenfelder are not 100% clear about this, simply saying we never see something partially observed:

That however does not imply something else is not going on during the observation. We know decoherence is going on, but as Sabine explains, this just gives an explanation of what the outcomes are and their probabilities, not how a particular outcome occurs. That is a black box. What is going on in that black box we do not know at this epoch in our knowledge of QM. It may even be nature is simply just like that - no further explanation required. Only further research can say.

The answer to the question depends on the interpretation. The answer by @Nugatory is correct from the standard minimal point of view.

Demystifer is correct. Different interpretations have different answers to that black box. The standard minimalist interpretation leaves it up for grabs so to speak - but some are more explicit - however that is for the interpretations sub-forum - not here.

Thanks
Bill
 
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All quantum mechanical interactions are black boxes. There is moment when we have the pre-interaction state, there is a later moment when we have the post-interaction state, but the theory says nothing about what happens in between.
There is something that happens in between, even if it is impossible to "observe" by experiment, to make massive particles into massless ones. There is something deeper than just wave functions, operators, and expected values. Nature is not random only not fully appreciated.
 
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Nugatory
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There is something that happens in between,
Why must be that be the case? The main reason we expect it to be that way is because we've spent all our lives surrounded by classical systems that work that way - but quantum mechanics says something different.

Now you may find this aspect of quantum mechanics to be deeply unsatisfying ("If that's the best answer QM has, then surely there must be something better!") and if so you're not alone. But unless and until someone comes up with a theory that works as well as QM and also says something useful about these hypothetical in-between states, we're just complaining that we don't like the answer without offering a better answer. QM is the way it is, and it really doesn't much care that not everyone likes it that way.

(I will ask the Bohmians to please remember that this is a B-level thread not in the Interpretations subforum and therefore withhold their malediction)
 
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But unless and until someone comes up with a theory that works as well as QM and also says something useful about these hypothetical in-between states, we're just complaining that we don't like the answer without offering a better answer. QM is the way it is, and it really doesn't much care that not everyone likes it that way.

Note - useful here would mean some kind of experimental confirmation such as the following:
https://arxiv.org/abs/quant-ph/0206196

I can't remember the problem with the above paper, but evidently there was an issue that invalidated it. But again this would not be for here - but the interpretations sub-forum. I merely mention it to show physicists are definitely looking at what that black box might be. It is not a particularly active area of research because QM works just fine as it is, but some are investigating it for sure. And if found a Nobel would be definitely be in play.

Thanks
Bill
 
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DennisN
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Nature is not random only not fully appreciated.
It would be cool if it weren't, but at the moment it at least looks to be very random at the atomic/subatomic scale.

Edit:

By the way, your comment reminded of that Einstein initially was critical of quantum mechanics, and famously said "God doesn't play dice."
Maybe he doesn't. Maybe he is busy at the roulette table instead. :)
 
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PeterDonis
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The answer to the question depends on the interpretation. The answer by @Nugatory is correct from the standard minimal point of view.

Which is the correct point of view for this forum. Discussions of particular QM interpretations belong in the interpretations subforum.
 
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PeterDonis
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There is something deeper than just wave functions, operators, and expected values.

As noted, discussions of QM interpretations, which are different attempts to provide "something deeper", belong in the interpretations subforum.
 
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As noted, discussions of QM interpretations, which are different attempts to provide "something deeper", belong in the interpretations subforum.
Here comes the fuzz.
 

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