Scalarized black holes in new massive gravity dressed by a nonminimally coupled scalar

Abstract

AbstractWe investigate scalarized black holes in new massive gravity dressed by a nonminimally coupled scalar. For this purpose, we find the Gregory–Laflamme (GL) and tachyonic instability bounds of bald BTZ black hole expressed in terms of $$m^2$$ m 2 a massive spin-2 parameter and $$\alpha $$ α a scalar coupling parameter to Ricci scalar by making use of the linearized theory around black hole. On the other hand, we obtain a solution bound of $$0.161<\alpha <3/16$$ 0.161 < α < 3 / 16 for achieving non-BTZ black holes with scalar hair analytically and a thermodynamic bound of $$1/8<\alpha <13/80$$ 1 / 8 < α < 13 / 80 for obtaining consistent thermodynamic quantities. Without imposing the GL instability bound $$(m^2<1/2\ell ^2),$$ ( m 2 < 1 / 2 ℓ 2 ) , we find a very narrow bound of $$0.161<\alpha <0.1625$$ 0.161 < α < 0.1625 which is located inside tachyonic instability bound of $$\alpha >1/8+m^2_{\Phi } \ell ^2/6$$ α > 1 / 8 + m Φ 2 ℓ 2 / 6 for obtaining scalarized black holes where $$m^2_{\Phi }$$ m Φ 2 is a scalar mass parameter.