# Origin of charge

1. Apr 28, 2010

### Leon_of_Vinci

Recently i have been looking into antimatter and also elementary particles, and i have began to wonder where exactly does charge come from. My thoughts often come to the idea of rotation direction, where negative is say... clockwise, and positive anticlockwise. that like gears two objects rotating the same direction would reject each other, while gears turning clockwise and anticlockwise turn together. I do not know how much proof/disproof is available, and i was wondering if there were any like minded people, or if I'm way off the mark :uhh: .

2. Apr 28, 2010

### Leon_of_Vinci

oops wrong forum i think

3. Apr 28, 2010

### Mu naught

I'm not sure anyone knows the true answer to this. Charge is such a fundamental property of matter, it's like asking where does mass come from (although we might actually have an answer for that soon).

It's also not accurate to think of particles as little spinning balls, because in fact they aren't balls at all but are also characterized by waves. It's a nice idea, but it really won't work if you think about it more.

4. Apr 28, 2010

### Leon_of_Vinci

where did i say balls... i get what your saying but simply deeming something undefinable is mistake (or at least that's how i see it). I guess the gear annalogy pointed towards, a ball bearing method but that's not exactly the way i meant it (just the easiest way to get across my idea). But just by looking at what little info i have to select from it appears that all matter should be comprised of the same base unit. rotation fits the description best (as it applies to both spinning and to waves) and it would allow for different charges while using the same "unit" of matter.

5. Apr 28, 2010

### Mu naught

If you're just making an abstraction to say "here's a way to think of a property that can lead to positive and negative quantities" then that's fine I suppose, but if you're trying to say that rotation is a source of charge, then I would say that's very likely to be wrong. I'm really not even sure what it would mean to have an electron "rotating".

6. Apr 28, 2010

### Leon_of_Vinci

well of course you know of the wave nature of matter (assuming) every massive object has a wave length equal to plank's constant over mass and velocity and much has been said about the wave nature of matter yadda yadda, but anyway rotation has a dual meaning as i noted in my previous post a rotation can mean.... one sec ill draw something (attached, not was drawn in paint).

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7. Apr 29, 2010

### haael

Yeah! Here's where Kaluza-Klein comes in hand!

According to Kaluza-Klein, charge is nothing more but momentum component in fifth dimension. As this dimension is curled, the charge is quantized. Electric current naturally occurs in energy-momentum tensor then. When you do Lorentz transformation and charge starts moving, a magnetic force appears as spatial components of electromagnetic field vector.
Also, electromagnetic vector itself is one "column" of metric tensor, linking 4d spacetime with fifth dimension, and that's why electromagnetic interaction couples charge to 4d momentum (i.e. charged particles change 4d momenta depending of EM field).
Fine structure constant comes up as the "size" of fifth dimension.

All of this comes from geometry alone. It's so cool, it must be true :).

8. Apr 29, 2010

### tom.stoer

But unfortunately there is not even a tiny hint that there are other dimensions than the four we currently observe :-)

9. Apr 29, 2010

### haael

Planck scale is still a bit far, so we can't hope for any direct experiment that would judge out existence of other dimensions. However, we will be able to deduce it sooner from particle spectrum.

Also, fact that gravity and electrodynamics can be derived from one simple principle is a strong hint for me. Even time can not be observed as a dimension directly. We call it a dimension, because special relativity works. If Kaluza-Klein worked, we should believe in existence of fifth dimension as well.

Finally, Kaluza-Klein is just too cool to be untrue :). It's the strongest proof for me :).

10. Apr 29, 2010

### tom.stoer

What about the other forces, el.-weak + QCD? So far no derivation from theories with extra dimensions.

Another question: the topology of the fifth dimension is fixed. Is this a stable solution taking into account the singularity theorems of Hawking & Penrose?

11. Apr 29, 2010

### Leon_of_Vinci

not that i'm denying the existence of a fifth... but what is it? length, width, depth, time... what? even time is still up in the air.

12. Apr 29, 2010

### haael

Length, width, depth, time, charge (yeah). Seriously, why do we need a specific name? It's just the fifth dimension.

First of all, you can make any gauge theory by adding a manifold of extra dimensions homeomorphic to gauge group. It's not very elegant, but it works.

In a more civilized way: EW is not that hard to embed into KK. Fifth dimension might be actually hypercharge or something. Even dilaton can provide Higgs mechanism, I read.

As for QCD - indeed I did not hear of any nice theory. However, I would be satisfied if for the next century QCD was just a field theory on a KK background.
Not very unlike Standard Model. It's also just EW+QCD forcefully glued up.

I don't know.

Any theory has some weaknesses. KK is not some paradox-free magical book. It just stands for its simplicity and elegance. One simple assumption leads to a cascade of theses so that Standard Model emerges naturally.
Don't rush. Kaluza-Klein will show it's glory some day.

13. Apr 30, 2010

### tom.stoer

The problem is that in all theories with extra dimensions (string theory is the most prominent one) the gauge structure in 4-dim. depends crucially on the topology of the extra dimensions (this already the case for KK with el.-mag. interaction + gravity). The more complex the gauge group becomes, the more complex the toplogy of the extra dimensions become.

That means you trade the demand to explain a specific gauge group for the demand to explain a specific fixed topology. I don't think that this new problem is easier to solve or more elegantly to handle. I think it's even a step backwards as it requires a fixed topology (or even geometry, namely the size of the extra dimensions), which contradicts all lessons we learned from GR.

So instead of turning gauge theory into some extension of GR / geometry, I prefer to turn GR into gauge theory; look at Poincare gauge theory, Einstein-Cartan theory and Ashtekar-Barbero formulation of loop quantum gravity. You do not (yet) have a unification of forces, but you have a unification of the mathematical framework.

But as long as there is no evidence for or against all these approaches, it is a matter of taste ...

14. Apr 30, 2010

### Redbelly98

Staff Emeritus
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