We complete the classification of Mink 4 solutions preserving N = 2 supersymmetry and SU(2) Rsymmetry parameterised by a round S 2 factor. We consider eleven-dimensional supergravity and relax the assumptions of earlier works in type II theories. We show that, using chains of dualities, all solutions of this type can be generated from one of two master classes: an SU(2)-structure in M-theory and a conformal Calabi-Yau in type IIB. Finally, using our results, we recover AdS 5 × S 2 solutions in M-theory and construct a compact Minkowski solution with Atiyah-Hitchin singularity.
IntroductionSome of the most physically relevant solutions in supergravity are those exhibiting a warped Minkowski factor. From early on, the main reason for this is that Minkowski vacua of string and M-theory are required to make contact with known particle physics phenomena in four dimensions, where one should arrange for the co-dimensions to be compact. Another reason, which clearly gained considerable traction with the advent of the AdS/CFT correspondence, is that all AdS solutions admit a description in terms of a foliation of Minkowski over a non compact interval -namely the Poincaré patch.The most simple way to realise a Minkowski vacua from ten or eleven dimensions is to assume that the compact internal space accommodates some holonomy group, specifically SU(3) or G 2 for compactifications of string theory or M-theory down to four dimensions respectively. Such solutions preserve (at least) N = 2 supersymmetry and have been well studied in the literature [1][2][3][4][5], with a resurgence of interest in the G 2 case in recent years [6-9] (see also [10][11][12][13] for G 2 arising in a heterotic context). However, such manifolds support neither fluxes nor a warping of the Minkowski directions, so it is reasonable to expect that they represent a rather small region of the space of possible solutions. The inclusion of fluxes requires one to generalise the notion of holonomy group to structure group (or G-structure) [14][15][16][17]. It is well known that no compact regular solutions of this type exist [18-20] -indeed a necessary element of such constructions are localised singularities, namely O-planes and their generalisations through string dualities, or lifts to M-theory (e.g. Atiyah-Hitchin singularities). Most progress constructing compact solutions with fluxes has happened within another restrictive ansatz, with the internal space assumed to be conformally a holonomy manifold [21][22][23], allowing one to broadly use the same mathematical tools as before. At this point all Mink d solutions for d > 1 (with the exception of Mink 2 in eleven dimensions) have been classified (see [24][25][26][27][28] for eleven dimensions, [29][30][31][32][33][34][35][36] for ten dimensions), however finding solutions beyond the ansatz of warped holonomy has proved challenging -see [38,39] for success in this direction. The issue appears to be one of tractability, so it would be helpful to have some additional guiding principle.AdS solutions necessita...