Surface defects in the D4 $-$ D8 brane system
Giuseppe Dibitetto, Nicolò Petri
TL;DR
The work constructs a new class of BPS flows in minimal $d=6$ $F(4)$ gauged supergravity with a running $2$-form, producing $AdS_3$-foliated geometries that asymptote to $AdS_6$ and uplift to warped $AdS_3\times S^2\times S^3$ solutions in massive IIA. Interpreted holographically, these flows describe surface defects (a $\mathcal{N}=(0,4)$ SCFT$_2$) within the $\mathcal{N}=2$ SCFT$_5$ dual to the $AdS_6\times S^4$ vacuum, arising from a D4-D8 brane system with a bound state of D2–NS5–D6 ending on it. The paper provides explicit analytic BPS solutions across four 6d backgrounds (with $M_3=\mathbb{R}^{1,2}$ or $AdS_3$ and $\Sigma_2=\mathbb{R}^2$ or $S^2$), their massive IIA uplifts, and a concrete holographic test via defect-induced one-point functions that match perturbative expectations. Overall, the results illuminate how AdS$_3$ slicing captures low-energy defect physics in higher-dimensional SCFTs and suggest links to lower-dimensional gauged supergravities describing similar defects. The constructions advance defect holography by connecting brane intersections to precise AdS$_3$-foliated loci within AdS$_6$ backgrounds and their IIA uplifts.
Abstract
A new class of exact supersymmetric solutions is derived within minimal $d = 6$ $F(4)$ gauged supergravity. These flows are all characterized by a non-trivial radial profile for the 2-form gauge potential included into the supergravity multiplet. In particular three solutions within this class are featured by an $\mathrm{AdS}_3$ foliation of the 6d background and by an $\mathrm{AdS}_6$ asymptotic geometry. Secondly, considering the simplest example of these, we give its massive IIA uplift describing a warped solution of the type $\mathrm{AdS}_3\times S^2\times S^3$ fibered over two intervals $I_r \times I_ξ$ . We interpret this background as the near-horizon of a D4 $-$ D8 system on which a bound state D2 $-$ NS5 $-$ D6 ends producing a surface defect. Finally we discuss its holographic dual interpretation in terms of a $\mathcal{N} = (0, 4)$ SCFT$_2$ defect theory within the $\mathcal{N} = 2$ SCFT$_5$ dual to the $\mathrm{AdS}_6\times S^4$ massive IIA warped vacuum.
