Universality of colored scalars from the stringy Kawai-Lewellen-Tye kernel

A new perspective on the inverse string theory Kawai-Lewellen-Tye (KLT) kernel is provided which establishes the universality of scattering amplitudes in the biadjoint scalar theory, pions in the nonlinear sigma model (NLSM), and mixed amplitudes (NLSM+<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msup><a:mi>ϕ</a:mi><a:mn>3</a:mn></a:msup></a:math>) recently studied in the literature. We show that all these amplitudes can be viewed as equivalent, arising from a single function, the inverse string theory KLT kernel, evaluated at different kinematic points. In this way cubic colored scalars and pions become interchangeable through a procedure we call the <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:msup><c:mi>α</c:mi><c:mo>′</c:mo></c:msup></c:math> shift. The latter complements the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>δ</e:mi></e:math> shift proposed by Arkani-Hamed , and demonstrates an inherent equivalence of scattering amplitudes in different quantum field theories by embedding them in a common stringy framework.