Multidimensional gravity, black holes and mirror (topological) stars

Abstract: We discuss static, spherically symmetric solutions to the 5D Einstein-Maxwell equations (belonging to wide classes of multidimensional solutions known at least from the 1990s) and select among them those which must observationally look like local objects whose surface reflects back particles or signals getting there, the so-called mirror stars (also called ``topological stars'' by some authors). Their significant parameters are the Schwarzschild mass $m$ and the magnetic charge $q$, such that $q^2 > 3m^2$. For comparison, we also discuss their black hole counterparts for which $q^2 < 3m^2$. For both these objects, we study spherically symmetric time-dependent perturbations and determine the stability regions in their parameter spaces. Our stability results disagree with some of those previously announced in the literature.