Ghostbusters: unitarity and causality of non-equilibrium effective field theories
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13130_2020_Article_12573.pdf
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Author(s)
Gao, Ping
Glorioso, Paolo
Liu, Hong
Date Issued
March 2020
Journal
Journal of High Energy Physics
Publisher
Springer Science and Business Media LLC
Citation
Gao, Ping et al. "Ghostbusters: unitarity and causality of non-equilibrium effective field theories." Journal of High Energy Physics 2020, 3 (March 2020): 40
Version
Final published version
Abstract
Abstract: For a non-equilibrium physical system defined along a closed time path (CTP), a key constraint is the so-called largest time equation, which is a consequence of unitarity and implies causality. In this paper, we present a simple proof that if the propagators of a non-equilibrium effective action have the proper pole structure, the largest time equation is obeyed to all loop orders. Ghost fields and BRST symmetry are not needed. In particular, the arguments for the proof can also be used to show that if ghost fields are introduced, their contributions vanish.
MIT Department
Massachusetts Institute of Technology. Center for Theoretical Physics
Terms of Use
Creative Commons Attribution
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DOI of Published Version
https://doi.org/10.1007/jhep03(2020)040
