Infinite quantum twisting at the Cauchy horizon of rotating black holes

Understand

We present a numerical calculation of the expectation value of the quantum angular-momentum current flux density for a scalar field in the Unruh state near the inner horizon of a Kerr-de Sitter black hole.

• Our results indicate that this flux diverges as $V_-^{-1}$ in a suitable Kruskal coordinate such that $V_-=0$ at the inner horizon.
• Depending on the parameter values of the scalar field and black hole that we consider, and depending on the polar angle (latitude), this flux can have different signs.
• In the near extremal cases considered, the angle average of the expectation value of the quantum angular momentum current flux is of the opposite sign as the angular momentum of the background itself, suggesting that, in the cases considered, quantum effects tend to decrease the total angular momentum of the spheres away from the extremal value.