Charge

[RonHughes]

Anyone have any ideas about the cause of charge. My own idea has turned out to be wrong or at least flawed. I would like to hear some of the members thoughts on the subject. The electron has some mechanism that causes charge while the proton has another. Doesn't logic dictate that what ever causes the charge of the electron would be the same for the proton but somehow opposite?

[lawcat]

Firstly, it important to begin the discussion by understanding that your very question goes against the prevailing view of what charge is.

The prevailing view is that charge is a fundamental property of some particles.

Your question presumes that something causes charge, which would make charge not fundamental in particles, but would make something else in particles fundamental so that charge is exhibited as an effect under certain conditions.

[Southtown]

Nicely put. Could Al's chirality argument pertain mayhaps.

 

http://www.fqxi.org/community/forum/topic/467

[RonHughes]

The electron is a particle? Does that particle have any sort of structure? If not what is it, just some kind of ephemeral ghost? Something about the electron causes it's charge. Just saying its fundamental does NOT explain why it has charge.

[CraigD]

The electron is a particle?

According to the presently best accepted physic, the Standard Model or particle physics, yes.

 

Does that particle have any sort of structure? If not what is it, just some kind of ephemeral ghost?

According to the SM, the electron has no internal structure, and thus no meaningful size or shape.

 

An electron is not “ephemeral”, in that it’s not short-lived. It’s not “ghostly”, as the probability of it being in an arbitrarily small volume of space with or an arbitrarily small range of velocities (but not both at the same time – see the Heisenberg uncertainty principle), and how it interacts with other particle can be calculated precisely.

 

Another important thing that electrons and other particles are not, are tiny bodies, like planets or pool balls, described exactly by the classical mechanics. They are described by quantum mechanics.

 

Something about the electron causes it's charge. Just saying its fundamental does NOT explain why it has charge.

The SM does not explain why some particles in it have electric or any of the several other kinds of charge or other quantum number value with which it describes them, and others do not, by requiring that each discrete quantum number be have a distinct cause. Rather, it names the know combination of quantum numbers, as particles, predicts how they interact with other particles, and gives conservation laws that describe how they can be transformed into one another.

 

These conservation laws can be considered “why” particles have charge, as they require that transformations of a particle with zero electric charge into two particles, one with non-zero electric charge, require that the sum of the particles charge be zero, and the sum of their energy to equal that of the original particle. Thus, we could say that, because a neutral boson such a photon has zero charge, and can interact with charged particles, such as quarks in a nucleon, to produce a positron with charge +1 and an electron, that the electron's -1 charge is required by the SM’s interaction and conservation laws (for more on this example, see pair production).

 

IMHO, the most important thing to understand about electric charge under the SM is that particles with charge interact with, and thus can interact with one another via, photons.

 

The electron has some mechanism that causes charge while the proton has another. Doesn't logic dictate that what ever causes the charge of the electron would be the same for the proton but somehow opposite?

I don’t think logic dictates this, any more than it dictates that if a 1 kg box or rocks gets its mass from rocks, a 1 kg box of apples must also get its mass from rocks.

 

The SM states that protons get their charge from their 3 constituent quarks: 2 up quarks, each with a charge of +2/3, and one down quark with a charge of -1/3.

 

I would like to hear some of the members thoughts on the subject.

My thoughts are that, while I don’t completely understand the SM, what I do understand of it, and the opinions of people who understand it better than me, leads me to consider it the best explanation of the electric charge and other quantum numbers it describes for various particles.

 

I think it’s important that people interested in fundamental physics questions like “what it the cause of charge?” to learn the SM thoroughly. The SM is a complete or “final theory”, but with the exception of gravity, it seems predictive with greater accuracy than any experiment can measure, which means FOPP perfectly predictive.

 

IMHO, The SM has completely addressed electric charge, but must be extended, modified, or completely replaced to describe gravity. I think this is the greatest challenge facing current physics.

Edited August 18, 2011 by CraigD
Fixed grammar mistake

[RonHughes]

I understand that position. If the world is considered flat by the mainstream then there is no reason to question that belief without impeccable proof to the contrary. Most of the worlds population continued believing the world was flat even after Magellan's expedition circumnavigated the world. So I guess calling the electron's charge fundamental is sufficient for the majority but I find it unsatisfactory.

[Qfwfq]

Doesn't logic dictate that what ever causes the charge of the electron would be the same for the proton but somehow opposite?

Logical enough...

 

Your question presumes that something causes charge, which would make charge not fundamental in particles, but would make something else in particles fundamental so that charge is exhibited as an effect under certain conditions.

Yes, like for instance there being a coupling constant in the interaction term between the field for the particle species in question and the field for the photon (which as you might guess is the electromagnetic field), which coupling constant is also often regarded as the Lie algebra generator of the quite trivial Lie group [imath]SU(1, \mathbb{C})[/imath], which is the particle's gauge symmetry group.

 

Could Al's chirality argument pertain mayhaps.

nah, no chance

 

Most of the worlds population continued believing the world was flat even after Magellan's expedition circumnavigated the world.

It is a widespread misconception, even that most folks believed it flat before those days.

[lawcat]

Yes, like for instance there being a coupling constant in the interaction term between the field for the particle species in question and the field for the photon (which as you might guess is the electromagnetic field), which coupling constant is also often regarded as the Lie algebra generator of the quite trivial Lie group [imath]SU(1, \mathbb{C})[/imath], which is the particle's gauge symmetry group.

 

What comes first, the chicken or the egg, the field or the charge?

[Qfwfq]

What comes first, the chicken or the egg, the field or the charge?

There is a slight grammatical error in there. You shuold write fields.

 

Before there are at least two (IOW more than one) fields how could there be an interaction term between "them" and besides, if you have only the fermionic field what would the local gauge symmetry be describing an interaction with? A ghost?

 

If an electron is in a region where the EM field is identically zero (granting this would make sense) it may as well have no charge. Your implicit modus tollens appeared to challenge the idea that

charge is exhibited as an effect under certain conditions.

Would you really deny this? In any case, because we say it has a charge regardless, you might say that therefore the charge comes first, but it being in a region where the EM field is zero is not the same as there being no such a thing as the EM field. The model shouldn't be dependent on when the field is zero or isn't.

 

In the end it's all a semantic issue. What do you guys mean when you say it is a fundamental particle? In my books this means it is non composite, which is associated with the assertion that there is no radial distribution to its mass-charge density. It also means that, in the model, it needs to be defined as a particle species (whereas a hadron's description can, at least could in principle, be derived from those of all involved constituent species). So what are you trying to tell this guy? Did God say "Let there be charge." instead of "Let there be light."? :rolleyes:

[lawcat]

To your last question, I do not know who mentioned fundamental "particle." I was discussing fundamental "properties."

 

As far as the former question, my understanding is,if the EM field is zero where particle is (not in the center of particle but next to it),then the particle is a non charged type of particle. In other words, if there is a charged particle, then there is electric field in case of static charge, and magnetic field in case of moving charge.

[Qfwfq]

To your last question, I do not know who mentioned fundamental "particle." I was discussing fundamental "properties."

Well then what do you mean by fundamental properties, then.

 

In the end, we don't know whether or not there is something that the SM can be based on although lots of folk have tried their hand at finding clues. So currently all we can really do is to chuck interaction terms into the Lagrangian, with a coupling constant, according to observed phenomenology, that's all. No point discussing fried air.

 

if the EM field is zero where particle is (not in the center of particle but next to it),then the particle is a non charged type of particle.

I wasn't talking about the particle's own field. Besides, your point just further shows that it can't have charge without an EM field existing, as well as the field for its own type.

[lawcat]

Fundamental, meaning essential, meaning in its essence "some" particles have charge as their essential property. Those particles that have charge generate electric field as a consequence of charge, and generate magnetic field when moving.

[Qfwfq]

Those particles that have charge generate electric field as a consequence of charge, and generate magnetic field when moving.

This is putting it at a much less fundamental level than how current particle physics puts it.

 

In any case it makes sense to assign coupling constants once an interaction term has been put in for a given fermion-boson pair, with a given gauge group. If you talk about electron and the weak bosons you have different charges (distinct from the electron's electric charge), if you talk about electron and gluon the constants are zero. If you talk about quarks and photons, the constants are in units of a third of that for leptons and photons. Oddly enough, quark confinement contstrains a hadron's electric charge to total an integer number of the lepton-photon units, IOW multiples of three of the quark-photon units. It all works out so neatly that one either believes in a very clever God who so chose things to be, or one tries to find an underlying mechanism from which it follows of necessity.

[RonHughes]

Are there anti-quarks?

[CraigD]

Are there anti-quarks?

Yes.

 

This is kinda a lazy question, though, something you should have answered on your own. :naughty:

 

As I wrote earlier,

I think it’s important that people interested in fundamental physics questions like “what it the cause of charge?” to learn the SM thoroughly.

I think it’d be good for you, Ron, to take some time with an introductory references or encyclopedia article (its wikipedia article is pretty good) and learn the basics of the Standard Model. Your hypo friends would help out – we could have a thread on it – and likely learn some new stuff in the process.

 

A nice thing about the SM is it’s small – there are only 16 fundamental particles in it (17 if you include the Higgs boson, which you don’t need when beginning), only 5 of which are needed for ordinary atomic physics. IMHO, it’s way easier to learn than basic chemistry, about as hard as the rules of chess, and somewhat similar. :)

 

You need not accept the SM as a perfect model (in fact, as I’ve explained previously, it’s got well-known, obvious limitations) any more than you accept chess as a realistic model of medieval warfare, but IMHO, the SM, like chess, is one of those things you need to “play” to really begin to understand.

[RonHughes]

Wow Craig, your chess metaphor was awesome. I will do as you suggest, thank you.

[Qfwfq]

Are there anti-quarks?

Yes.

Are there anti-photons?

Yes. Except that they're the exact same species as photons. Yup, this is a more corrrect reply than if someone said there's no such thing as anti-photons. This is inherent in using relativistic quantum field theory for describing any, literally any particle species.

 

To give your question a simpler answer, it is: Yes, and they are distinct species.

 

...any more than you accept chess as a realistic model of medieval warfare

Jease, I'd say there's quite a gap, no comparison. SM describes particle physics much more accurately than chess describes any warfare, with the tiny exception of a duel over a fine young lady in Marostica. Which other battles does chess accurately model?

 

I think the main, most relevant thing is to say that we don't know if there is a more fundamental model which SM follows from of necessity, but there could well be and nobody could rule it out.