Absorption cross section of regular black holes in scalar-tensor conformal gravity

In terms of the complex angular momentum method, we compute the absorption cross section by analyzing a massless test scalar field around conformally related black holes. First, we investigate circular null geodesics and thereby prove a precondition for calculating the absorption cross section in the context of conformally related black holes. Then we use the WKB approximation method to derive the analytic expression of Regge frequency and the oscillation part of absorption cross sections. We find that this oscillation part depends on the scale factor of conformal transformations. By taking the conformally related Schwarzschild-Tangherlini black hole as an example, we show that this regular black hole has substantially distinctive absorption behavior compared with singular black holes. Our result provides a new approach to distinguish a regular black hole from a singular one.

Automated summary

Using the complex angular momentum method, we calculate the absorption cross section by analyzing a massless test scalar field around conformally related black holes. We find that the oscillation part of the absorption cross sections depends on the scale factor of conformal transformations and demonstrate substantial differences in absorption behavior between a regular black hole and a singular one using the conformally related Schwarzschild-Tangherlini black hole as an example. Our study provides a new approach to distinguish between regular and singular black holes.