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arXiv · 1509.02169

New Representations of the Perturbative S-Matrix

Christian Baadsgaard·N. E. J. Bjerrum-Bohr·Jacob L. Bourjaily·Simon Caron-Huot·Poul H. Damgaard·Bo Feng
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Abstract

We propose a new framework to represent the perturbative S-matrix which is well-defined for all quantum field theories of massless particles, constructed from tree-level amplitudes and integrable term-by-term. This representation is derived from the Feynman expansion through a series of partial fraction identities, discarding terms that vanish upon integration. Loop integrands are expressed in terms of "Q-cuts" that involve both off-shell and on-shell loop-momenta, defined with a precise contour prescription that can be evaluated by ordinary methods. This framework implies recent results found in the scattering equation formalism at one-loop, and it has a natural extension to all orders---even non-planar theories without well-defined forward limits or good ultraviolet behavior.

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Christian Baadsgaard, N. E. J. Bjerrum-Bohr, Jacob L. Bourjaily, Simon Caron-Huot, Poul H. Damgaard, Bo Feng. 2015-09-07. New Representations of the Perturbative S-Matrix. https://doi.org/10.1103/physrevlett.116.061601

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