Related papers: Ringing and echoes from black bounces surrounded b…
In this work, we investigate relativistic tidal forces around a black hole sourced by a cloud of strings, described by the generalized Letelier-Alencar solution. We first review the original Letelier spacetime and its recent generalization,…
This study investigates a black hole surrounded by a cloud of strings and a cosmological dark fluid characterized by a modified Chaplygin-like equation of state (MCDF), $p=A\rho-B/\rho^{\beta}$. We analyze its geodesic structure, shadow,…
Massive fields can exist in long-lived configurations around black holes. We examine how the gravitational wave signal of a perturbed black hole is affected by such `dirtiness' within linear theory. As a concrete example, we consider the…
Exact solutions which generalize the Bardeen black hole solution, in the sense that several sources are taken into account, are derived. The most general case corresponds to a charged Bardeen black hole with a cosmological constant and…
The string equations of motion and constraints are solved for a ring shaped Ansatz in cosmological and black hole spacetimes. In FRW universes with arbitrary power behavior [$R(X^0) = a\;|X^0|^{\a}\, $], the asymptotic form of the solution…
We demonstrate that strings near the horizon of a Schwarzschild black hole, when viewed by a stationary observer at infinity, probe a string Carroll geometry, where the effective lightspeed is given by the distance from the horizon. We…
We study the emergence of string instabilities in $D$ - dimensional black hole spacetimes (Schwarzschild and Reissner - Nordstr\o m), and De Sitter space (in static coordinates to allow a better comparison with the black hole case). We…
In classical General Relativity (GR), an observer falling into an astrophysical black hole is not expected to experience anything dramatic as she crosses the event horizon. However, tentative resolutions to problems in quantum gravity, such…
The recent detections of gravitational waves from binary systems of black holes are in remarkable agreement with the predictions of General Relativity. In this pedagogical mini-review, I will go through the physics of the different phases…
The spectrum of the quasinormal modes of the gravitational waves emitted during the ringdown phase following the merger of two black holes is of primary importance in gravitational astronomy. However, the spectrum is extremely sensitive to…
Scientists collaborating internationally have developed a new way to learn about our universe through gravitational waves, which are ripples in space-time caused by the motion and vibration of celestial bodies. By analogy, gravitational…
Exotic compact objects may resemble black holes very closely while remaining horizonless. They may be distinguished from black holes because they effectively give rise to a resonant cavity for the propagation of low frequency gravity waves.…
In this paper, we concern about applying general relativistic tests on the spacetime produced by a static black hole associated with cloud of strings, in a universe filled with quintessence. The four tests we apply are precession of the…
Extreme 4-dimensional dilaton black holes embedded into 10-dimensional geometry are shown to be dual to the gravitational waves in string theory. The corresponding gravitational waves are the generalization of pp-fronted waves, called…
Cosmic strings inside Schwarzschild black holes in teleparallel gravity are considered.Torsion flux inside the black hole is compute like a torsion vortex on a superfluid.Since some components of torsion are singular on Schwarzschild…
The existence of black holes and of spacetime singularities is a fundamental issue in science. Despite this, observations supporting their existence are scarce, and their interpretation unclear. We overview how strong a case for black holes…
Gravitational wave echoes may appear following a compact binary coalescence if the remnant is an "exotic compact object" (ECO). ECOs are proposed alternatives to the black holes of Einstein's general relativity theory and are predicted to…
A distorted black hole radiates gravitational waves in order to settle down in one of the geometries permitted by the no-hair theorem. During that relaxation phase, a characteristic damped ringing is generated. It can be theoretically…
Black holes are the hydrogen atoms of quantum gravity. For instance solving the information loss paradox will likely require a deep understanding of how the long-sought quantum gravity theory works. In this thesis we explore how black holes…
One class of competitive candidates for dark matter is ultralight bosons. If they exist, these bosons may form long-lived bosonic clouds surrounding rotating black holes via superradiant instabilities, acting as sources of gravity and…