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Author Topic: What field are particle wavefunctions in?  (Read 1505 times)

Martin Fennell

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What field are particle wavefunctions in?
« on: 26/03/2011 23:30:02 »
Martin Fennell asked the Naked Scientists:
   
Hi,

Thanks for a great podcast.

Investigating Quantum Physics with my 12 year old son, we learn that each particle has an associated wavelength.

My question is -

What field are the wavefunctions in? Are they always electromagnetic waves, or something else?

Thanks

Martin

What do you think?
« Last Edit: 26/03/2011 23:30:02 by _system »


 

Offline JMLCarter

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What field are particle wavefunctions in?
« Reply #1 on: 27/03/2011 00:05:27 »
The wave-functions are not field oscillations in themselves. If the particle in question has charge or colour there will be a corresponding field oscillations.

Unfortunately the answer is a little more complicated. Some say that one can never intuitively understand quantum mechanics, and this is one example of where it gets a bit other-worldly.

The square of a wave-function describes the probability distribution of the particle in space. So wave functions are square-roots of probability distributions - if that is a type of entity that has some "real meaning" to any-one I would love to know, but I fear not.

People tend to fall into two camps, firstly there's those that say it is something real, but outside our intuitive capabilities (one has to do the math to get a grip on it), secondly there's those who say something yet to be explained is going on, and a wave-function is just a mathematical model that we will have to make do with for now.

Experiment shows it works pretty well though.
 

Offline yor_on

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What field are particle wavefunctions in?
« Reply #2 on: 27/03/2011 02:16:36 »
The wave function is a mathematical model describing how we think waves 'moves'. It's about what 'states' a wave can be in before it interacts with a detector/observer.

There are two 'main' camps as I see it. Either you trust in that at some point a wave function collapse through its interaction with a 'observer' (and why we use a 'observer', is the idea that to really 'know' that it stops being in a superposition someone has to be there to 'observe/measure' it. Although anything could be a 'observer/detector' it's only when we notice it that we can say it 'exist' and that is the approach taken as I understands it). and that's what I think of as the Copenhagen interpretation (Bohr) in where you don't discuss if the wave function is a 'real thing' in itself but only what, and how, a wave does. That is, how it finalize itself in a interaction, as described by the model, like that photon hitting your eye, interacting finalizing itself. And the way it is before interacting is undefined as per 'Heisenberg's uncertainty principle' which states that you can't, ever, know all there is needed to know about, well, anything in fact at the quantum level At least not enough to making you able to say how the particle really 'is', as well as what's going to happen. Instead you have to look at the probability of it, the photon being in a undefinable 'superposition' before interacting.

A superposition in this context means that the wave only can be defined by its probability of becoming, in fact not being able to be defined at all, and therefor also possible to view as it has all possibilities coexisting, as long as there is no 'interaction' finalizing it.

The other way is Feynman's in where the wave function becomes defined by all paths possible, with our wave taking them all simultaneously. But as the paths gets combined mathematically some of them will fall away due to their 'probability amplitudes' quenching each other or reinforcing each other and when you sum up the amplitudes of all the different paths (sum over histories) then the only path that survives will be the one that the particle actually follows.

It's two ways to the same end. Nowadays it seems that people finds Feynman's definition the easier to stomach, as it doesn't involve HUP (Heisenberg's uncertainty principle) as the Copenhagen interpretation does.

But to me 'sum over paths) is just as mysterious as it uses the idea that all paths somehow has to be taken for this to happen. Without those paths being taken for real, there is no 'probability amplitudes' to interfere with each other :) Not that I mind, I've always enjoyed magic :) or 'sleight of hands' if you like.

So if your son wants to become a fully practicing arcane master of the 'arts' :) he's made a head start asking about this. And you too :)
« Last Edit: 27/03/2011 02:51:35 by yor_on »
 

Offline yor_on

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What field are particle wavefunctions in?
« Reply #3 on: 27/03/2011 02:31:53 »
As for each particle having a certain wave?
Is it 'matter waves' you are thinking of there?

That's an idea from 1923, by Louis de Broglie. "matter, he suggested, actually consists of waves."  If your son would like a cool site about Quantum mechanics in general, and matter waves, look  H e r e.
 

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What field are particle wavefunctions in?
« Reply #3 on: 27/03/2011 02:31:53 »

 

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