The D8-Brane Tied up: String and Brane Solutions in Massive Type IIA Supergravity

TL;DR

This work studies Romans' massive type IIA supergravity, where a mass parameter $m$ (dual to a 10-form sourced by a D8-brane) introduces mass terms for the NSNS 2-form $B$ and the RR 7-form $C^{(7)}$. The authors construct two explicit 1/4-BPS solutions: a massive string configuration describing the intersection of a fundamental string with a D8-brane over a D0-brane, and a massive D6-brane configuration describing the intersection of a D6-brane with a D8-brane over a NSNS 5-brane, each supported by nonzero $B$ or $C^{(7)}$ and governed by a harmonic-function–type ansatz via a function $ar{Ω}$. In both cases, the solutions reduce to their massless counterparts (F-string and D6-brane) and preserve $1/4$ of the supersymmetries, despite involving three objects; the results highlight the nontrivial role of $m$ and the D8-background in brane intersections. The findings provide concrete realizations of D8-background intersections in massive IIA, suggest possible higher-dimensional origins, and outline directions for discovering additional massive IIA solutions.

Abstract

We present two new solutions of Romans' massive type IIA supergravity characterized by the two non-trivial massive potentials of Romans' theory: the NSNS 2-form and the RR 7-form. They can be interpreted respectively as the intersection of a fundamental string and a D8-brane over a D0-brane and the intersection of a D6-brane with a D8-brane over a NSNS5-brane. The D8-brane manifests itself through the mass parameter and in the massless limit one recovers the standard fundamental string and D6-brane solutions. Although these solutions do not have the usual form for BPS bound states at threshold and each of them involves 3 objects, both of them preserve 1/4 of the supersymmetries.