Black hole binaries and light fields: gravitational molecules.

We show that light scalars can form quasi-bound states around binaries. In the non-relativistic regime, these states are formally described by the quantum-mechanical Schrodinger equation for a one-electron heteronuclear diatomic molecule. We performed extensive numerical simulations of scalar fields around black hole binaries showing that a scalar structure condensates around the binary - we dub these states "gravitational molecules". We further show that these are well-described by the perturbative, non-relativistic description.