Gravity seminar : Marcelo Salgado, Instituto de Ciencias Nucleares — Scalar Clouds and Rotating Hairy Black Holes (BH)

I will focus mainly in describing (neutral) cloud solutions around Kerr BH, where the complex-valued scalar field that characterizes
these solutions is a test field in such a background spacetime. Then the corresponding solutions for the full Einstein-Klein-Gordon system is presented (the backreaction of the field into the spacetime is now taken into account) for stationary, axisymmetric, circular and asymptotically flat spacetimes. Such solutions represent rotating hairy BH. The talk will be divided in three parts: in the first one I setup the problem. In the second part I provide some motivations, alluding to the no-hair conjecture and no-hair theorems. Finally, in the 3rd part I will show the numerical analysis, and a heuristic argument that allows one to understand why the existing no-hair theorems for the above system in spherical symmetry cannot be extended to the rotating scenario, and therefore, justify in a conceptual manner the existence of such clouds and hairy solutions. Finally, I will comment about the open problems in this direction and the perspectives for the future.