Graviton Scattering: Compute Amplitudes w/Einstein Gravity

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    Graviton Scattering
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Discussion Overview

The discussion centers on the possibility of computing scattering amplitudes for graviton interactions within the framework of Einstein gravity as an effective field theory at low energies. Participants explore the relationship between quantum gravity and general relativity, as well as the implications of detecting gravitons versus gravitational waves.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the feasibility of computing graviton scattering amplitudes, suggesting that quantum gravity may not align well with general relativity.
  • Another participant notes that while gravitational waves have been detected, isolating a graviton remains unachieved, indicating the graviton is a predicted but undetected particle.
  • A different viewpoint asserts that it is indeed possible to compute these amplitudes, likening the process to the refraction of gravitational waves and emphasizing the need for low-energy conditions due to the nonlinearity of general relativity at higher energies.
  • Some participants agree that quantum gravity can be approximated by an effective field theory at long distances, with certain diagrams related to graviton scattering being computable and commonly assigned as homework in graduate studies.
  • References to review articles by Donaghue and Burgess are provided to support the discussion on the topic.

Areas of Agreement / Disagreement

Participants express differing views on the compatibility of quantum gravity with general relativity, with some asserting that computations are possible while others remain skeptical. The discussion does not reach a consensus on the feasibility of computing graviton scattering amplitudes.

Contextual Notes

Participants highlight the limitations in understanding the relationship between quantum gravity and general relativity, particularly regarding the detection of gravitons and the conditions under which effective field theory applies.

PedroBittar
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Is it possible to compute scattering amplitudes of a graviton interaction taking Einstein gravity as an effective field theory at low energies?
I did not study qft the proper way yet, so any clarifications on the subject would be welcome.
 
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I don't know much about scattering, but quantum gravity (and gravitons) does not seem to cooperate with GR. So probably not.
 
So far my limited knowledge on the topic, until now, we were only able to detect gravitational waves (and this was not an easy task) but unable to isolate a graviton. The graviton is a undetected predicted particle.
 
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Yes, this should be possible. We would refer to it as refraction of the gravitational waves, just as we do with light whenever individual photons are not relevant. To translate to "graviton density", simply divide the energy flow of the waves by ωħc.
A low-energy condition is necessary not so much because of quantum effects, but because at higher energies the nonlinearity of GR itself makes the wave description fall apart.
 
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The answer is yes, quantum gravity is well approximated at long distances by an effective field theory of gravitation. A particular diagram or class of diagrams (like graviton scattering) are readily computable and are often homework problems given to grad students in this field.

See some of the famous review articles by Donaghue or Burgess:
like eg:
https://arxiv.org/abs/gr-qc/0311082v1
 
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Haelfix said:
The answer is yes, quantum gravity is well approximated at long distances by an effective field theory of gravitation. A particular diagram or class of diagrams (like graviton scattering) are readily computable and are often homework problems given to grad students in this field.

See some of the famous review articles by Donaghue or Burgess:
like eg:
https://arxiv.org/abs/gr-qc/0311082v1
Thank you!
 

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