N=8 non-BPS Attractors, Fixed Scalars and Magic Supergravities
S. Ferrara, A. Marrani
TL;DR
This work analyzes the Hessian of the black hole potential $V_{BH}$ in $ ext{N}=8$, d=4 supergravity, focusing on non-BPS critical points and their stability, and connects these results to the $ ext{N}=2$ magic supergravities obtained via consistent truncations. The authors derive attractor equations and characterize the Hessian spectra for the $rac{1}{8}$-BPS and non-BPS branches, showing a rank of $30$ for the $rac{1}{8}$-BPS Hessian and a model-dependent, representation-driven splitting for non-BPS points, governed by embeddings into $ ext{USp}(8)$ and its subgroups. They map the $ ext{N}=8$ spectra to $ ext{N}=2$ descendants, clarifying how vector- and hypermultiplet scalars reorganize into $ ext{N}=2$ multiplets and how the well-known $n_V+1$ / $n_V-1$ degeneracy pattern for generic special Kahler geometries arises in this higher-dimensional context. Through explicit analyses of the magic models $ ext{J}_{3}^{ ext{H}}, ext{J}_{3}^{ ext{C}}, ext{J}_{3}^{ ext{R}}, ext{stu}, ext{J}_{3,M}^{ ext{R}}, ext{J}_{3,M}^{ ext{C}}$, the paper demonstrates how the Hessian eigenstructure and stability properties are inherited under $ ext{N}=8 ightarrow ext{N}=2$ reductions, including cases with and without flat directions. The results offer a coherent picture of non-BPS attractors across extended supergravities and highlight practical routes for extending the analysis to non-maximal theories.
Abstract
We analyze the Hessian matrix of the black hole potential of N=8, d=4 supergravity, and determine its rank at non-BPS critical points, relating the resulting spectrum to non-BPS solutions (with non-vanishing central charge) of N=2, d=4 magic supergravities and their ``mirror'' duals. We find agreement with the known degeneracy splitting of N=2 non-BPS spectrum of generic special Kahler geometries with cubic holomorphic prepotential. We also relate non-BPS critical points with vanishing central charge in N=2 magic supergravities to a particular reduction of the N=8, 1/8-BPS critical points.
