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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Black-hole spectroscopy is a powerful tool to probe the Kerr nature ofastrophysical compact objects and their environment. The observation ofmultiple ringdown modes in gravitational waveforms could soon lead tohigh-precision gravitational-wave spectroscopy, thus it is critical tounderstand if the quasinormal mode spectrum itself is affected by astrophysicalenvironments, quantum corrections, and other generic modifications. In thischapter, we will review the black-hole spectroscopy program and its challengesregarding quasinormal mode detection, the overtone status and the recentevidence that supports the existence of nonlinearities in the spectrum of blackholes. We will then discuss a newly introduced non-modal tool in black-holephysics, namely the pseudospectrum; a mathematical notion that can shed lighton the spectral stability of quasinormal modes, and discuss its novelapplications in black holes and exotic horizonless compact objects. We willshow that quasinormal modes generically suffer from spectral instabilities,explore how such phenomena can further affect black-hole spectroscopy, anddiscuss potential ringdown imprints and waveform stability issues in currentand future gravitational-wave detectors.

Black-hole spectroscopy: quasinormal modes, ringdown stability and the pseudospectrum