Eikonal quasinormal modes and shadow of string-corrected d-dimensional black holes

We compute the quasinormal frequencies of d-dimensional spherically symmetric black holes with leading string alpha' corrections in the eikonal limit for tensorial gravitational perturbations and scalar test fields. We find that, differently than in Einstein gravity, the real parts of the frequency are no longer equal for these two cases. The corresponding imaginary parts remain equal to the principal Lyapunov exponent corresponding to circular null geodesics, to first order in alpha'. We also compute the radius of the shadow cast by these black holes. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

In this study, we calculated the quasinormal frequencies of d-dimensional spherically symmetric black holes with leading string alpha' corrections for tensorial gravitational perturbations and scalar test fields. We found that, in contrast to Einstein gravity, the real parts of the frequency are no longer equal for these two cases, but the corresponding imaginary parts remain equal to the principal Lyapunov exponent corresponding to circular null geodesics.