(I wrote this using the assumption that the graviton exists, which I know is not necessarily true; this is asked from a theoretical standpoint)

It is my understanding that General Relativity states all massive and/or energetic particles must be affected by the curvature of spacetime; this stipulation aligns with all known elementary particles. I understand that the graviton, being a particle that reliably interacts with photons, is going to be virtually impossible to detect experimentally. It is almost certainly massless and of a remarkably low energy, but it must possess energy nonetheless. As such, shouldn't gravitons themselves be affected by gravity, creating a paradox in which (increasingly virtual ?) gravitons must interact with other gravitons? Also, assuming that our conception that massless particles always travel at the speed of light holds true for gravitons, wouldn't gravitons themselves not be able to escape from a black hole, annulling the gravitational force of the black hole in the process?

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    $\begingroup$ I don't see where the paradox is. Gluons self-interact too. Also, possible duplicate of How does gravity escape a black hole? and links therein. $\endgroup$ Jun 29 '19 at 17:24
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    $\begingroup$ Photons are also massless, but black holes can have electric and magnetic fields. $\endgroup$
    – G. Smith
    Jun 29 '19 at 18:11
  • $\begingroup$ @AccidentalFourierTransform it is my current understanding that, in QFT, electric fields can be thought of in terms virtual photons, and that this conceptualization should theoretically extend to all of the fundamental forces, including gravity. Shouldn’t this mean that gravitons emitting from a massive object must be affected by a slightly more virtual graviton, which in turn must be affected by an slightly more virtual graviton than that, so on and so forth? Anyways, I’m grateful for the link; I’ll dig into it when I get a chance. Cheers! $\endgroup$ Jun 29 '19 at 19:42
  • $\begingroup$ @G.Smith wait... what? How? $\endgroup$ Jun 29 '19 at 19:43
  • $\begingroup$ @QuaternionsRock Your picture of gravitons being affected by virtual gravitons is not wrong. The formalisation of that intuition is what we call the loop expansion. There is nothing paradoxical about that. $\endgroup$ Jun 29 '19 at 19:54

Yes, gravitons must necessarily respond to each other via gravity. This means that in addition to communicating forces between objects that bend spacetime, the force carrier particles bend spacetime themselves.

But for very weak gravitational fields, the math gets easier to deal with because in this simplified case, the effect of the gravitons themselves on the curvature of spacetime can be ignored.

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    $\begingroup$ This is how the subject is described in the book the ideas of particle physics. If this is wrong, then what is the right answer? $\endgroup$ Jun 30 '19 at 0:58
  • $\begingroup$ @safesphere, thanks for the reference, see my just-posted question. $\endgroup$ Jun 30 '19 at 4:00
  • $\begingroup$ answer edited per your comments and those of g. smith $\endgroup$ Jun 30 '19 at 4:55

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