The researchers work in quantum gravity, a field that seeks to understand gravitational forces through quantum mechanics. In their new paper, published March 17 in the journal Physical Review Letters , Calmet and his colleagues found that black holes may indeed have hair, albeit very subtle hair. In this way, the quantum information pertaining to that matter is preserved, giving the black hole its hair. If correct, this would mark a momentous advance in theoretical physics. Researchers speaking to BBC News claim to have resolved the paradox with a theorem that black holes have "quantum hair," or imprints in their gravitational fields left by components of the stars that formed them.