Worldsheet construction of Romans massive type IIA supergravity

Develop a direct worldsheet construction of a string theory whose low-energy limit is Romans massive type IIA supergravity.

Background

Romans massive type IIA supergravity describes AdS vacua separated by D8-branes, but a direct worldsheet formulation of a string theory yielding Romans supergravity as its low-energy limit is lacking. The paper instead studies setups in type IIA on S1/Z_2 (type I') where Romans supergravity appears as part of the background with orientifold 8-planes and D8-branes.

A worldsheet construction would provide a fundamental microscopic definition of massive type IIA, complementing existing effective and background-based descriptions.

References

While we do not have direct world-sheet construction of a string theory whose low energy limit is given by Romans supergravity, the latter appears as part of the background in type IIA string theory compactified on $S1/Z_2$, with orientifold 8-planes at the two ends and 16 D8-branes placed at various points along $S1/Z_2$.

— Exotic Branes and Symmetries of String Theory (2512.19068 - Sen, 22 Dec 2025) in Section 5.3 (D8-branes in type I' string theory)