Black hole spontaneous scalarisation with a positive cosmological constant

Understand

A scalar field non-minimally coupled to certain geometric [or matter] invariants which are sourced by [electro]vacuum black holes (BHs) may spontaneously grow around the latter, due to a tachyonic instability.

• This process is expected to lead to a new, dynamically preferred, equilibrium state: a scalarised BH.
• The most studied geometric [matter] source term for such spontaneous BH scalarisation is the Gauss-Bonnet quadratic curvature [Maxwell invariant].
• This phenomenon has been mostly analysed for asymptotically flat spacetimes.