A review is given on the foundations and applications of non-Hermitian classical and
quantum physics. First, key theorems and central concepts in non-Hermitian linear algebra …

Very compact objects probe extreme gravitational fields and may be the key to understand
outstanding puzzles in fundamental physics. These include the nature of dark matter, the …

The dawn of the twenty-first century came with very positive prospects for gravity, cosmology,
and astrophysics. Technological progress made it possible for cosmology to enter to its …

Black hole spectroscopy is the program to measure the complex gravitational wave
frequencies of merger remnants, and to quantify their agreement with the characteristic …

AIM, UMR 7158, CEA/DRF, CNRS, Université Paris Diderot, Irfu/Service d'Astrophysique,
Centre de Saclay, FR-91191 Gif-sur-Yvette, France

It is commonly believed that the ringdown signal from a binary coalescence provides a
conclusive proof for the formation of an event horizon after the merger. This expectation is …

The Bardeen black hole holds historical significance as the first model of a regular black
hole. Recently, there have been proposed interpretations of the Bardeen spacetime as …

In general relativity, when two black holes merge they produce a rotating (Kerr) black hole
remnant. According to perturbation theory, the remnant emits “ringdown” radiation; a …

The existence of black holes and spacetime singularities is a fundamental issue in science.
Despite this, observations supporting their existence are scarce, and their interpretation is …

The LIGO/Virgo detections of binary black hole mergers marked a watershed moment in
astronomy, ushering in the era of precision tests of Kerr dynamics. We review theoretical and …