This article is intended to review the recent developments in the Horndeski theory and its
generalization, which provide us with a systematic understanding of scalar–tensor theories …

After a decade and a half of research motivated by the accelerating universe, theory and
experiment have reached a certain level of maturity. The development of theoretical models …

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 …

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 …

One century after its formulation, Einstein's general relativity (GR) has made remarkable
predictions and turned out to be compatible with all experimental tests. Most of these tests …

A bstract It was shown recently that the static tidal response coefficients, called Love
numbers, vanish identically for Kerr black holes in four dimensions. In this work, we confirm …

One of the most promising strategies to test gravity in the strong-field, large curvature regime
is gravitational spectroscopy: the measurement of black hole quasinormal modes from the …

General relativity has passed all solar system experiments and neutron star based tests,
such as binary pulsar observations, with flying colors. A more exotic arena for testing …

We derive the quadratic action for the physical degrees of freedom of massless spin-0, spin-
1, and spin-2 perturbations on a Schwarzschild-(A) dS background in arbitrary dimensions …

Gravitational spectroscopy—the measurement of the quasi-normal modes of a black hole
from the ringdown signal of a binary black hole coalescence—is one of the most promising …