Spherically symmetric black holes with electric and magnetic charge in extended gravity: Physical properties, causal structure, and stability analysis in Einstein's and Jordan's frames

Understand

Novel static black hole solutions with electric and magnetic charges are derived for the class of modified gravities: $f({\cal R})={\cal R}+2\beta\sqrt{{\cal R}}$, with or without a cosmological constant.

• The new black holes behave asymptotically as flat or (A)dS space-times with a dynamical value of the Ricci scalar given by $R=\frac{1}{r^2}$ and $R=\frac{8r^2\Lambda+1}{r^2}$, respectively.
• They are characterized by three parameters, namely their mass and electric and magnetic charges, and constitute black hole solutions different from those in Einstein's general relativity.
• Their singularities are studied by obtaining the Kretschmann scalar and Ricci tensor, which shows a dependence on the parameter $\beta$ that is not permitted to be zero.