Heterotic black horizons

Abstract

We show that the supersymmetric near horizon geometry of heterotic black holes is either an AdS ₃ fibration over a 7-dimensional manifold which admits a G ₂ structure compatible with a connection with skew-symmetric torsion, or it is a product ${\mathbb{R}^{1,1}} \times {\mathcal{S}^8}$, where ${\mathcal{S}^8}$ is a holonomy Spin(7) manifold, preserving 2 and 1 supersymmetries respectively. Moreover, we demonstrate that the AdS ₃ class of heterotic horizons can preserve 4, 6 and 8 supersymmetries provided that the geometry of the base space is further restricted. Similarly ${\mathbb{R}^{1,1}} \times {\mathcal{S}^8}$ horizons with extended supersymmetry are products of ${\mathbb{R}^{1,1}}$ with special holonomy manifolds. We have also found that the heterotic horizons with 8 supersymmetries are locally isometric to AdS ₃ × S ³ × T ⁴, AdS ₃ × S ³ × K ₃ or ${\mathbb{R}^{1,1}} \times {T^4} \times {K_3}$, where the radii of AdS ₃ and S ³ are equal and the dilaton is constant.