On the trivalent junction of three non-tachyonic heterotic string theories

Abstract

Recently, Altavista, Anastasi, Angius and Uranga discussed a method to construct junctions and bouquets of different perturbative string theories. Following this analysis, we here argue that three non-tachyonic ten-dimensional heterotic string theories can be joined together at a nine-dimensional junction. This is done by creating a two-dimensional non-conformal $\mathcal{N}{=}(0,1)$ supersymmetric quantum field theory with three asymptotic ends, each equipped with one of the worldsheet theories of the supersymmetric $E_8\times E_8$ theory, the supersymmetric $SO(32)$ theory, and the non-supersymmetric $SO(16)\times SO(16)$ theory, respectively. It is actually a special case of a more general construction involving an arbitrary $\mathbb{Z}_2$-symmetric theory $T$, its $\mathbb{Z}_2$-orbifold $T/\mathbb{Z}_2$, and the modified $\mathbb{Z}_2$-orbifold $(T\times q)/\mathbb{Z}_2$, where $q$ is a certain $\mathbb{Z}_2$-symmetric spin invertible theory.