https://doi.org/10.1140/epjs/s11734-025-01804-8
Review
Coordinate light-cone-ordered perturbation theory
C. N. Yang Institute for Theoretical Physics and Department of Physics and Astronomy, Stony Brook University, 11794-3840, Stony Brook, NY, USA
a
george.sterman@stonybrook.edu
Received:
19
February
2025
Accepted:
8
July
2025
Published online:
4
August
2025
We review the development of light-cone-ordered perturbation theory in coordinate space (C-LCOPT). Compared to light-cone-ordered perturbation theory in momentum space (LCOPT), the role of intermediate states in LCOPT is played in C-LCOPT by paths, which are ordered sequences of lines and vertices that connect pairs of external points. Each path denominator of C-LCOPT equals the difference between the separation of the minus coordinates of the beginning and ending points of the path and the sum of the light-cone distances of all lines along the path computed from their plus and transverse coordinates. We observe that this method, originally applied to amplitudes, can be extended to cross sections, which are given in terms of closed paths reminiscent of Schwinger–Keldysh formalisms.
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Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
