Janus and Hades in M-theory
Multi-parametric and analytic families of four-dimensional $\,\textrm{AdS}_{3} \times \mathbb{R}\,$ (Janus) and $\,\textrm{AdS}_{3} \,\times\, \mathbb{R}^{+}$ (Hades) solutions are constructed in the SO(8) gauged supergravity that arises from the consistent reduction of eleven-dimensional supergravity on $\,\textrm{S}^7\,$. The solutions are generically non-supersymmetric, involve non-trivial running scalars and preserve a $\,\textrm{U}(1)^4\,$ symmetry. Different patterns of (super) symmetry enhancement occur upon suitable adjustment of the free parameters which further control the boundary conditions of the running scalars. We concentrate on the non-supersymmetric Janus and Hades solutions with $\,\textrm{SU}(3) \times \textrm{U}(1)^2\,$ symmetry and provide their higher-dimensional description in terms of M-theory fluxes and membranes. Special attention is paid to a class of such Hades solutions dubbed "ridge flows" which resemble dielectric rotations of Coulomb branch flows previously investigated in the literature.