Black Holes in Massive Dynamical Chern-Simons gravity: scalar hair and quasibound states at decoupling

Understand

Black holes have a unique sensitivity to the presence of ultralight matter fields or modifications of the underlying theory of gravity.

• In the present paper we combine both features by studying an ultralight, dynamical scalar field that is nonminimally coupled to the gravitational Chern-Simons term.
• In particular, we numerically simulate the evolution of such a scalar field around a rotating black hole in the decoupling approximation and find a new kind of massive scalar hair anchored around the black hole.
• In the proximity of the black hole, the scalar exhibits the typical dipolar structure of hairy solutions in (massless) dynamical Chern-Simons gravity.