English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

It is shown here that the extraction of quasinormal modes (QNMs) within thefirst Born approximation of the scattering amplitude is mathematically not wellfounded. Indeed, the constraints on the existence of the scattering amplitudeintegral lead to inequalities for the imaginary parts of the QNM frequencies.For instance, in the Schwarzschild case, $0 \leq \omega_I < \kappa$ (where$\kappa$ is the surface gravity at the horizon) invalidates the poles deducedfrom the first Born approximation method, namely, $\omega_n = i n \kappa$.

Comment on "Quasinormal modes in Schwarzschild-de Sitter spacetime: A simple derivation of the level spacing of the frequencies"