Positive Geometry for Stringy Scalar Amplitudes
arXiv:2508.20161 · doi:10.1103/lb5l-twsb
Abstract
We introduce a new positive geometry, the associahedral grid, which provides a geometric realization of the inverse string theory KLT kernel. It captures the full -dependence of stringified amplitudes for bi-adjoint scalar theory, pions in the NLSM, and their mixed / amplitudes, reducing to the corresponding field theory amplitudes in the limit. Our results demonstrate how positive geometries can be utilized beyond rational functions to capture stringy features of amplitudes, such as an infinite resonance structure. The kinematic -shift, recently proposed to relate field theory and NLSM pion amplitudes, naturally emerges as the leading contribution to the stringy geometry. We show how the connection between and NLSM can be geometrized using the associahedral grid.
5+2 pages, 4 figures; v2: minor mistake in End Matter corrected, matches published version
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