Titlebook: What is the iε for the S-matrix?; Holmfridur Sigridar Hannesdottir,Sebastian Mizera Book 2022 The Author(s), under exclusive license to Sp

隱士

https://doi.org/10.1007/978-3-031-18258-7Scattering Matrix; Feynman integrals; QFT and Causality; Anomalous thresholds; Landau equation; Schwinger

能夠支付

集合

Conclusion,This chapter concludes the book with a summary of the results and a list of open questions.

混合

Holmfridur Sigridar Hannesdottir,Sebastian MizeraProvides a pedagogical introduction to the analytic properties of the S-matrix.Reviews the rich literature on singularities of scattering amplitudes.Presents a new prescription for analytically contin

Ischemic-Stroke

Unitarity Implies Anomalous Thresholds, the analytic structure of the cuts. We discuss the implications of the cutting rules when unstable particles are involved in the scattering process: we derive how to cut through dressed propagators, and show that cuts through undressed propagators for unstable particles resum to zero.

悠然

Primer on the Analytic S-matrix,elop intuition and illustrate the key points relevant for general multi-loop diagrams. Throughout this chapter, we point out which facets of the analysis generalize straightforwardly and which are more intricate.

BAIT

Intrepid

Branch Cut Deformations,cuts can be deformed away to restore the connection between the upper- and lower-half planes, and one when they cannot. Finally, we explain how summing over different Feynman diagrams might result in incompatible . prescriptions and one is forced to consider branch cut deformations to define the complexified amplitude in the first place.

peptic-ulcer

,Glimpse at?Generalized Dispersion Relations, any . scattering process. We find two types of identities: the first relates the scattering amplitude to an integral over its discontinuity, while the second relates parts of the scattering amplitude to an integral over its imaginary part.

–DOX