Stokes Polytopes and Intersection Theory

Abstract

Intersection numbers of Stokes polytopes living in complex projective space are computed using the techniques employed to find the inverse string KLT matrix elements in terms of intersection numbers of associahedra. To do this requires an appropriate convex realization of Stokes polytopes in $\mathbb{CP}^{n}$ loaded with suitable generalizations of the Koba-Nielsen factor. The procedure is carried out explicitly for the lower point cases and the prescription for the generic higher point cases is laid out as well. The intersection numbers are identified as scattering amplitudes corresponding to a theory the coupling constants of which are determined entirely in terms of the combinatorial weights of the Stokes polytopes. A parameter $\alpha'$ having units of length is used to define the intersection numbers in a manner that yields the amplitudes of $\phi^4$ theory to leading order when the limit of vanishing $\alpha'$ limit is taken. Most importantly, we contrast this method of understanding quartic vertices with previous string-theoretic attempts to obtain quartic interaction amplitudes and highlight the advantages offered.