Ward Identity and Scattering Amplitudes for Nonlinear Sigma Models.

Ian Low,Zhewei Yin

doi:10.1103/physrevlett.120.061601

Abstract

We present a Ward identity for nonlinear sigma models using generalized nonlinear shift symmetries, without introducing current algebra or coset space. The Ward identity constrains correlation functions of the sigma model such that the Adler's zero is guaranteed for S-matrix elements, and gives rise to a subleading single soft theorem that is valid at the quantum level and to all orders in the Goldstone decay constant. For tree amplitudes, the Ward identity leads to a novel Berends-Giele recursion relation as well as an explicit form of the subleading single soft factor. Furthermore, interactions of the cubic biadjoint scalar theory associated with the single soft limit, which was previously discovered using the Cachazo-He-Yuan representation of tree amplitudes, can be seen to emerge from matrix elements of conserved currents corresponding to the generalized shift symmetry.

Highlights

Ward Identity and Scattering Amplitudes for Nonlinear Sigma ModelsWe present a Ward identity for nonlinear sigma models using generalized nonlinear shift symmetries, without introducing current algebra or coset space
Introduction.—Nonlinear sigma models [1] have wide-ranging applications in many branches of physics
The Ward identity constrains correlation functions of the sigma model such that the Adler’s zero is guaranteed for S-matrix elements, and gives rise to a subleading single soft theorem that is valid at the quantum level and to all orders in the Goldstone decay constant

Summary

Ward Identity and Scattering Amplitudes for Nonlinear Sigma Models

We present a Ward identity for nonlinear sigma models using generalized nonlinear shift symmetries, without introducing current algebra or coset space. The Ward identity constrains correlation functions of the sigma model such that the Adler’s zero is guaranteed for S-matrix elements, and gives rise to a subleading single soft theorem that is valid at the quantum level and to all orders in the Goldstone decay constant. Interactions of the cubic biadjoint scalar theory associated with the single soft limit, which was previously discovered using the Cachazo-He-Yuan representation of tree amplitudes, can be seen to emerge from matrix elements of conserved currents corresponding to the generalized shift symmetry. [16] studied the subleading single soft limit of tree-level amplitudes in a variety of theories exhibiting Adler’s zeros using the Cachazo-He-Yuan (CHY) representation of scattering equations [17,18,19].

Published by the American Physical Society

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