All eight- and nine-dimensional string vacua from junctions
Mirjam Cvetič, Markus Dierigl, Ling Lin, Hao Y. Zhang
Abstract
String and 5-brane junctions are shown to succinctly classify all known 8D $\mathcal{N}=1$ string vacua. This requires an extension of the description for ordinary $[p,q]$-7-branes to consistently include $\mathrm{O}{7}^{+}$ planes, which then naturally encodes the dynamics of ${\mathfrak{sp}}_{n}$ gauge algebras, including their $p$-form center symmetries. Central to this analysis are loop junctions, i.e., strings/5-branes which encircle stacks of 7-branes and $\mathrm{O}{7}^{+}\mathrm{s}$. Loop junctions further signal the appearance of affine symmetries of emergent 9D descriptions at the 8D moduli space's boundaries. Such limits reproduce all 9D string vacua, including the two disconnected rank (1,1) moduli components.