https://doi.org/10.1140/epjc/s10052-023-12378-x
Regular Article – Theoretical Physics
Note on NLSM tree amplitudes and soft theorems
Center for Gravitation and Cosmology, College of Physical Science and Technology, Yangzhou University, 225009, Yangzhou, China
Received:
26
August
2023
Accepted:
23
December
2023
Published online:
22
January
2024
This note provides a new point of view for bootstrapping the tree amplitudes of the nonlinear sigma model (NLSM). We use the universality of single soft behavior, together with the double copy structure, to completely determine the tree amplitudes of the NLSM. We first observe Adler’s zero for four-point NLSM amplitudes, by considering kinematics. Then we assume the universality of Adler’s zero and use this requirement to construct general tree amplitudes of the NLSM in the expanded formula, i.e., the formula of expanding NLSM amplitudes to bi-adjoint scalar amplitudes, which allows us to give explicit expressions of amplitudes with arbitrary numbers of external legs. The construction does not require the assumption of quartic diagrams. We also derive double soft factors for NLSM tree amplitudes based on the resulting expanded formula, and the results are consistent with those in the literature.
© The Author(s) 2024
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