Orateur
Description
According to the Λ-Cold Dark Matter (ΛCDM) model, a positive cosmological constant explains
the accelerated expansion of the Universe. We start by constructing a static solution of general
relativity with a positive cosmological constant that consists of two (or more) static black holes
whose gravitational attraction is balanced by the cosmic expansion of the de Sitter background.
Then, we extend our analysis and establish the existence of stationary, spinning black binaries in a
de Sitter universe and analyse their properties (there is no quadrupole momenta, no radiation). We
consider identical black holes with either aligned or anti-aligned spins which maximize the spin-spin
repulsion or attraction, respectively. We discuss the prospect that spin-spin interactions can stabilize
the binaries. Our solutions establish continuous non-uniqueness in general relativity without matter
(we have several solutions with the same cosmological entropy and angular momentum) for the first
time in four dimensions. They evade assumptions of mathematical theorems that would otherwise
rule out their existence. They also provide initial data for the spinning binary merger problem (when
orbital angular momentum is added).
