Localized modes at a D-brane--O-plane intersection and heterotic Alice strings

Understand

We study a system of $N_c$ $D3$-branes intersecting $D7$-branes and $O7$-planes in 1+1-dimensions.

• We use anomaly cancellation and string dualities to argue that there must be chiral fermion zero-modes on the $D3$-branes which are localized near the $O7$-planes.
• Away from the orientifold limit we verify this by using index theory as well as explicit construction of the zero-modes.
• This system is related to F-theory on K3 and heterotic matrix string theory, and the heterotic strings are related to Alice string defects in $\mathcal{N}=4$ Super-Yang-Mills.