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I'm reading Quantum field theory in a Nutshell and I find a very interesting calculation that leads to the gravitational interaction between 2 light beam.

Is this kind of interaction permitted in general relativity? (not necessarily a quantum gravity theory or the like) Is there a energy tensor $T_{\mu\nu}$ asscociated with a photon so that it creates $R_{\mu\nu}\ne 0$? It's awesome if someone can give a simple derivation in the framework of general relativity.

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    $\begingroup$ Your photon is a disturbance in an EM field, which $T_{\mu\nu}$ corresponds to, so yes, you should get a non-zero energy-momentum tensor corresponding to the photon. $\endgroup$ – PPR Aug 16 '14 at 17:15
  • $\begingroup$ Can you explicitly deriving $T_\mu\nu$? Thanks! $\endgroup$ – Learning Aug 17 '14 at 0:52
  • $\begingroup$ possible duplicate of Do two beams of light attract each other in general theory of relativity? $\endgroup$ – John Rennie Aug 17 '14 at 10:43