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For a standard set of Feynman rules (following in-out formalism) in momentum space, extracted from a generally given Lagrangian, is there a generic algorithm for converting them into the Feynman rules (following in-in formalism) in momentum space? What changes one must make for such conversion of rules for the propagators and vertices in momentum space?

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1 Answers1

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Yes, the main points are that the field content gets doubled up, and that the Feynman propagators are replaced with e.g. retarded and advanced propagators. For details, see e.g. Refs. 1-4.

References:

  1. R.D. Jordan, Phys. Rev. D 33 (1986) 444.

  2. C.R. Galley & M. Tiglio, arXiv:0903.1122 ; chap. III.

  3. M. Levi, arXiv:1807.01699; p. 49-50.

  4. G.U. Jakobsen, G. Mogull, J. Plefka & B. Sauer, arXiv:2207.00569; chap. 2 p. 10.

Qmechanic
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