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Basic questions about Gravitons 
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#1
Feb1313, 04:21 AM

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I have some basic questions about gravitons.
If you have two particles with mass, do they "exchange" gravitons, if so what is the frequency? 


#2
Feb1313, 06:42 AM

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#3
Feb1313, 08:08 AM

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How frequently do two particles with mass exchange gravitons, or if they are "broadcast" how frequently does a particle with mass emit gravitons?



#4
Feb1313, 08:35 AM

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Basic questions about Gravitons
I'm not sure the question means much in this context  it's not like the two masses are constantly firing gravitons at each other. See discussion:
http://www.physicsforums.com/showthread.php?t=15211 See how it works for photons: http://math.ucr.edu/home/baez/physic...particles.html 


#5
Feb1313, 09:18 AM

P: 10

Sorry Simon, I'm not framing the question coherently. Am I right in thinking that in a simple 1 star 1 planet model, the GR solution gives space as curved and the planet's orbit is the natural or straight path thru it. The QM solution uses gravitons as a messenger particle to tell the planet how to move thru space?
So in the GM model the larger the star, the greater the number of particles with mass, the greater the number of gravitons the planet receives? 


#6
Feb1313, 09:48 AM

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The 2nd of Simon's links above answers this (towards the bottom.) Virtual particles arise in perturbation theory, but since gravity is not renormalizable, there is no wellbehaved perturbation expansion to speak of. The role of virtual gravitons in establishing static gravitational fields is not implied by current theories.



#7
Feb1313, 10:06 AM

P: 308

That's a pretty strong statement. It is implied by standard QFT. Gravity isn't the only nonrenormalizable theory with a low energy perturbation expansion which is consistent. The low energy side has to be described by an effective field theory, regardless of the UV completion.
This discussion shows up at least every week or so on PF. I'm not sure why all the graviton hating :) 


#8
Feb1313, 10:56 AM

P: 10

Gravitons seems a complex solution, compared to curved space. Consider two galaxies in a local cluster if each particle with mass is interacting with every other via gravitons?
As gravity is rangeless, does that imply that every particle with mass in the universe is in a graviton exchange relation with every other mass particle? 


#9
Feb1313, 06:18 PM

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That is true for all charged particles as well. 


#10
Feb1413, 01:20 AM

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#11
Feb1513, 02:18 AM

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Shouldn't this be in "Beyond the Standard Model"?



#12
Feb1513, 06:41 AM

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Others have picked up on this too:
Related: I've been trying to find a reference for the rate of EM interactions ... a charged particle may move in a curved path in an electromagnetic field, which implies many successive interactions... seems legitimate to ask after the rate (possibly "mean rate") of the interactions which would be expected to depend on the field strength. I suspect I'm momentarily forgetting something obvious. 


#13
Feb1513, 11:38 AM

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#14
Feb1513, 09:18 PM

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Thanks Bill_K  a suspicion like that was behind my reply in post #4 and I suspect it is the core OPs original question.
The Feynman diagrams do make them look a bit like there should be a series of bumps don't they? But they are actually representations of some mathematical process? Which leads back into the nature of virtual particles. 


#15
Feb1613, 09:41 AM

P: 308

Feynman diagrams are just a way to draw the Taylor series of e^S, where S is the action (lagrangian) of the system. The action has parts that represent propagators and interactions. Expanding e^S gives a whole mess of combinations of such ingredients. Feynman diagrams are just a way of systematically accounting for all possible terms.



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