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I understand that the EM mediator is the photon and is absorbed and emitted by electrons. I understand that the strong force mediator is the gluon and is absorbed and emitted by quarks. Both electrons and quarks are pointlike elementary particles with rest mass.

If there are gravitons and they are the mediators for Gravity, which pointlike elementary particle with rest mass would absorb and emit them?

knzhou
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Árpád Szendrei
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1 Answers1

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All particles that are able to interact electromagnetically (not just electrons)can emit or absorb photons. So by definition if there was a graviton all particles that interact gravitationally could emit and absorb them. Your question gives the constraint of which particles with rest mass would emit/absorb gravitons. Mass is a measure of the particles involvement in gravitational interaction (like charge is a measure of involvement in the electromagnetic interaction). So all particles with rest mass would emit and absorb gravitons.

The question asks only about particles with rest mass, but in fact all particles would emit and absorb gravitons, not just those with rest mass. The source of gravitational fields is the stress-energy tensor, not rest mass. Roughly speaking, mass and energy and equivalent ($E=mc^2$), so energy participates in gravitational forces as well.

K. Kirilov
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  • please tell me about a specific particle other then the electron that can emit and absorb photons as a mediator of EM and a particle other then the quark that can emit and absorb a gluon as a mediator of strong force. – Árpád Szendrei Apr 07 '18 at 10:34
  • The positron (if you accept antimatter as an answer). And the nucleus as a whole, because it can occupy different energy levels and (though I'm unsure if we can interpret this as individual protons absorbing and emitting photons) – K. Kirilov Apr 07 '18 at 10:51
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    Anything with electric charge can emit photons. That includes quarks, Z bosons, any chemical ion, and so on. Similarly anything with "gravitational charge" can emit gravitons but that really means anything with energy. – knzhou Apr 07 '18 at 12:08
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    @knzhou Z are neutral, but in higher orders they can when interacting emit a photon. – anna v Apr 07 '18 at 12:35
  • @annav Whoops. I was typing too fast there, thanks! – knzhou Apr 07 '18 at 12:35
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    @ÁrpádSzendrei elementary particles that couple to strong interactions, can emit and absorb gluons in the appropriate boundary condition (within hadrons in our laboratory conditions) – anna v Apr 07 '18 at 12:37
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    So all particles with rest mass would emit and absorb gravitons. This is wrong. All particles would emit and absorb gravitons, not just those with rest mass. The source of gravitational fields is the stress-energy tensor, not rest mass. –  Apr 07 '18 at 14:22
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    @BenCrowell The question is about particles with rest mass, so I have constrained myself to them. I didn't claim particles with no rest mass will not emit/absorb gravitons. – K. Kirilov Apr 07 '18 at 14:26
  • Thank you so much! Can you please tell me, do gravitons theoretically create an attraction in a way that they get exchanged between particles, or do they get emitted by a particle and actually bend the fabric of spacetime itself? – Árpád Szendrei Apr 07 '18 at 15:54
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    @K.Kirilov: In that case, how about editing the answer? It's misleading in its present form. –  Apr 07 '18 at 16:14
  • @BenCrowell I kept my answer in the realm of what I am comfortable with and is enough to cover the original question. I intentionally avoided the more general claim because I am not yet all that familiar with the stress energy tensor and I don't know how it works together with quantum mechanics. Feel free to edit the answer if you think it's needed. – K. Kirilov Apr 07 '18 at 16:56
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    @K.Kirilov: OK, done. –  Apr 07 '18 at 18:02
  • @ÁrpádSzendrei : You appear to have a new Question. You should post it as a Question, not as a Comment. – Eric Towers Apr 07 '18 at 20:27
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    @BenCrowell I assume this means gravitons can emit gravitons right? – user541686 Apr 07 '18 at 20:35