Ho\v{r}ava-Witten theory on ${\mathbf{S}}^1\vee{\mathbf{S}}^1$ as type 0 orientifold

TL;DR

This paper explores dualities between M-theory compactifications on quantum geometries and type 0 orientifolds, revealing geometric explanations for features like gauge group doubling and novel degrees of freedom.

Contribution

It establishes a duality between Hořava-Witten theory on S^1∨S^1 and a 0B orientifold, providing geometric insights into orientifold characteristics and uncovering new M-theoretic degrees of freedom.

Findings

Relates Hořava-Witten theory to a 0B orientifold with SO(16)^4 gauge group.

Explains gauge group doubling through geometric duality.

Identifies emergent M-theoretic degrees of freedom at junction points.

Abstract

We investigate dualities between ${\mathbf{Z}}_2$ quotients of recently proposed compactifications of M-theory on `quantum geometries' of the form ${\mathbf{S}}^1\vee{\mathbf{S}}^1$ and 10d orientifolds of type 0A and 0B string theories. In particular, we relate the Ho\v{r}ava-Witten theory on ${\mathbf{S}}^1\vee{\mathbf{S}}^1$ to a 0B orientifold with gauge group $SO(16)^4$. The resulting dictionary provides a geometric explanation for characteristic features of the 0B orientifold, such as the doubling of the gauge group, while the perturbative spectrum of the 0B orientifold indicates the emergence of novel M-theoretic degrees of freedom associated with the junction point. The 0B orientifold further reveals the existence of two variants of the theory on ${\mathbf{S}}^1\vee{\mathbf{S}}^1$, corresponding to equal vs opposite (i.e., standard vs Fabinger-Ho\v{r}ava) orientations of the $E_8$ walls. We also analyze additional 0A and 0B orientifolds whose open string sectors do not arise from higher-dimensional gauge fields in M-theory and whose microscopic interpretation remains an open problem.