Is the existance of charged particles without rest mass theoratical possible?

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To a moderator:
I forgot to put the "d" after charge in the title, but I cannot edit it.
Can you please make the correction?
Thanks.

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Fixed it.

Concerning the original question, I suspect it depends on which Theory you are using here. We've never observed such a particle, and have no reason to think one exists. If it is massless, it is also momentumless, so it would be very quick to combine and neutralize a massive (or other massless) particle. There is also some question in my mind about what such a particle would do in the presence of a photon, since it would ride the wave very freely. The presence of such particles would make for some odd things.

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Thanks for that.

Lets use mainstream theory. Does such a particle e.g. fit in the standard model?

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No such particle(s) is/are included in the standard model.

Let me ask you a question though, If such a particle were to be in the presence of even the slightest charge imbalance, what would stop it from immediately accelerating to the speed of light, and heading toward (or away from) that charge. If there was such an instant acceleration of a charged particle, what wavelength of light would it give off when it moved?

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Photons are massless and have momentum. Massive and massless particles both obey the same equation,

E² - p²c² = m²c⁴,

the only difference being that m=0 for a massive particle. This means that the energy-momentum four-vector of a massive particle is time-like while the energy-momentum four-vector of a massless particle is null.
In the standard model the neutrino was massless and chargeless, at least chargeless as far as electromagnetic charge is concerned. On the other hand, neutrinos possessed lepton number, a different form of "charge". Of course now evidence points towards neutrinos having mass, so now the photon and the graviton are the only massless particles we can be sure of.

As far as I know, the photon and graviton carry no charges whatsoever, they are just carriers of energy, momentum and spin angular momentum. At the moment it appears that any particle carrying a charge will have some mass.

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Go ahead and correct your post. I know you didn't mean these two things.

Thanks for the clarification on momentum.

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I am really no expert, but I believe that in meanstream theory, massless particles must go with the speed of light, like photons.

On the other hand, when you look at the coulomb force and the gravitational force you see they are very similiar. What makes mass so special? Also, we know that all other combinations of charge-mass particles do exist. Why not this one?

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Thomas,

An electric field (and electromagnetic field) has energy associated with it (energy density ~E^2 + ~B^2). That corresponds to mass by E = mc^2, and indeed, any energy (and momentum) is a source term for gravity in Einstein's Field Equation. Accelerating charge radiates, and the resulting radiation reaction force acts like an inertial term, a mass of sorts.

So anything that "makes energy" has some mass associated with it. In the last century. The (in)famous 4/3mc^2 problem of classical electromagnetic theory shows this "inertia" vs mass energy equivalence doesn't exactly work out as expected -- something more is going on there, and quantum theory "does better" about this, but still isn't there completely.

In summary, energy makes gravity, and has inertia, so anything with energy is going to have mass, gravitational as well as inertial.

Now, about gravitons. Gravity makes gravity -- there's a self-interaction there. When gravitational radiation carries away energy from a system, that energy should make more gravity , so that would seem to suggest that a graviton has relativistic mass (at least "real gravitons" that carry radiation, not virtual ones -- but all this is just speculation because there is no succesful quantization of GR), and so should interact gravitationally.

This would be in contrast to a photon which has no charge and so isn't itself affected by charge.

-Richard

Except photons, right? (Disregarding pair creation)

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Thomas,

Remember it is zero *rest mass*, not zero relativistic mass. A photon has relativistic mass, energy and momentum, and means it makes a gravitational field. But these contributions are so ridiculously small that it is of a no consequence. But technically it is there.

For example, consider if by some process the entire mass of the earth was converted to radiation, and further somehow contained. That would be an absolutely unbelievable amount of energy density, and it would make the same gravity as it did when it was all rest mass.

Of course, nothing could contain that much radiation energy, and it would make a spectacular explosion, spreading the energy out and therefore the gravitational field it made.

And RussT, if you're reading this, the above ball of contained energy is similiar to the MECO/ECO model. That enormous radiation pressure of a huge amount of mass converted to radiation energy is what (they claim) holds off the collapse. But the gravity is so strong, it contains that enormous radiation energy density, and it only slowly radiates it away. It slowly collapses as it radiates, and takes orders of magnitude longer than age of the universe (I mean many orders) to get rid of that energy. That is what Mitra and company say, of course.

-Richard

I agree. And, correct me if I'm wrong, zero rest mass means the particle can only travel with the speed of light in vacuum (whatever that is ).

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That is correct. Massive particles follow time-like curves, massless particles follow null curves. Viewed locally a null curve corresponds to motion at c.

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The bar has been lowered for the promotion of ATM ideas; the bar for the acceptance of ATM ideas must remain high.

So, which of the curves you describe here, do Neutrinos follow?

Your answer of course will be...it depends on whether they have 'mass' or not.

If this 'mass' is Planck mass/energy/size, then what?

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RussT
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[That enormous radiation pressure of a huge amount of mass converted to radiation energy is what (they claim) holds off the collapse.]

This is exactly the same as a star, isn't it?

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RussT
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This is an excelent accounting of the situation, and because it is, highlights some of the key issues here!

[So anything that "makes energy" has some mass associated with it.]

This might be part of the problem...the mass part is certainly correct, but shouldn't the "makes energy" really be *converts energy*? (accept for the Gamma pair production, of course)

[energy makes gravity,]

Which would make this a little different, implying that the 'gravity' was already there?

[Now, about gravitons. Gravity makes gravity]

Which makes this?

Since, by defintion, gravity is directly measured by its mass content, how can it just make more if itself?

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RussT
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Everything is, as it should be, otherwise, it wouldn't be!

If you have energy, you have gravity. More correctly, energy creates spacetime curvature, which is gravity.

Not quite. In GR, gravity is the result of the amount of Stress-Energy. Stress-Energy is computed using the Stress-Energy tensor. This include the total mass (converted to energy through E=mc² along with the stress (or in GR, pressure).

The GR equations are non-linear. In simple terms,
1) an object has an amount of stress-energy, which creates a gravitational field.

2)This gravitational field has an energy, which create an additional amount of gravity.

3)This so called secondary amount of gravity has an energy, which create an additional amount of gravity.

4) etc, etc, etc.

What we think of as Newtonian gravity is simply 1 above. The precession of Mercury's perihelion is a second order effect, the result of non-linearity which can be thought of simply as 2 above.

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Russ,

This shows why precise language is needed sometimes, specifically the meaning of "make". I was using several shades of meaning there, I see now. Let me try to make this as clear as I can muster.

Mass is energy and energy has mass. That's the fundamental meaning of E=mc^2. What we call mass, which is sometimes sort of thought as "frozen energy" is just another form of energy. Me, I don't think of it as frozen. So any form of energy has mass, and therefore produces a gravitational field. There is no conversion from one form of energy to another needed. Energy is the source of the gravitational field.

Einstein's Field Equation (EFE) is written usually with the mc^2 as the T_00 term anyway, which means you deal