Comparing graphs in the imaginary time and real time formalisms

@inproceedings{Kobes1991ComparingGI,
  title={Comparing graphs in the imaginary time and real time formalisms},
  author={Randy Kobes},
  year={1991}
}
One-particle-irreducible graphs in the imaginary time formalism of finite temperature field theory differ in general with those of the real time formalism. A sum of graphs in the real time formalism is considered here, motivated by causality arguments, and in some one-loop examples agreement is found with the corresponding analytically continued imaginary time result.