Abstract: The anomalous decay rate of the quasinormal modes occurs when the longest-lived modes are the ones with a higher angular number. Such behavior has been recently studied in different static spacetimes for scalar and fermionic perturbations, being observed in both cases. In this work, we extend the existent studies to the charged spacetimes---namely, the Reissner-Nordstr\"om, the Reissner-Nordstr\"om de Sitter, and the Reissner-Nordstr\"om anti--de Sitter black holes. We show that the anomalous decay rate behavior of the scalar field perturbations is present for every charged geometry in the photon sphere modes, with the existence of a critical scalar field mass whenever $\mathrm{\ensuremath{\Lambda}}\ensuremath{\ge}0$. In general, this critical value of mass increases with the raising of the black hole charge, thus rendering a minimum in the Schwarzschild limit. We also study the dominant mode/family for the massless and massive scalar fields in these geometries, showing a nontrivial dominance of the spectra that depends on the black hole mass and charge.

... read more

Topics: Schwarzschild radius (59%), Scalar field (58%), Photon sphere (56%) ... read more

More

11 results found

••

Abstract: On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160) Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

... read more

Topics: Stellar black hole (81%), Rotating black hole (77%), Binary black hole (76%) ... read more

4,375 Citations

•••

Abstract: Recently, the anomalous decay rate of quasinormal modes has been studied for some geometries under scalar field perturbations, which occurs when the longest-lived modes are the ones with higher angular number, as well as the existence of a critical scalar field mass, i.e., the value of scalar field mass such that the decay rate does not depend appreciably on the angular number, and beyond which the behavior of the decay rate is inverted. Here, we consider the propagation of fermionic fields in the background of Schwarzschild--de Sitter black holes, and we show that the anomalous decay rate behavior and the fine structure, related to the coupling between the chirality and the mass of the field, can be observed in the fermionic spectrum.

... read more

Topics: Scalar field (61%), Schwarzschild radius (56%), Field (physics) (54%) ... read more

10 Citations

•••

Almendra Aragón^{1}, P. A. González^{1}, Eleftherios Papantonopoulos^{2}, Yerko Vásquez^{3}•Institutions (3)

Abstract: We study the propagation of scalar fields in the background of an asymptotically de-Sitter black hole solution in $f(R)$ gravity, with the aim of analyzing the existence of an anomalous behavior in the quasinormal modes (QNMs) spectrum in alternatives theories of gravity and to study the stability of the scalar field propagation. We study the QNMs for various overtone numbers of different branches that they depend on a parameter $\beta$ which appears in the metric and characterizes the $f(R)$ gravity. For small deviations from the Schwarzschild-dS black hole the anomalous behavior in the QNMs is present, and the critical value of the mass of the scalar field depends on the parameter $\beta$ while for large deviations the anomalous behavior does not appear. Also, the critical mass of the scalar field increases when the overtone number increases until the $f(R)$ gravity parameter $\beta$ approaches the near extremal limit at which the critical mass of the scalar field does not depend anymore on the overtone number. Also, we find that the imaginary part of the quasinormal frequencies is always negative for all branches leading to a stable propagation of the scalar fields in this background.

... read more

Topics: Scalar field (62%), f(R) gravity (60%), Scalar (mathematics) (57%) ... read more

7 Citations

•••

Almendra Aragón^{1}, P. A. González^{1}, Eleftherios Papantonopoulos^{2}, Yerko Vásquez^{3}•Institutions (3)

Abstract: We study the propagation of scalar fields in the background of an asymptotically de Sitter black hole solution in f(R) gravity. The aim of this work is to analyze in modified theories of gravity the existence of an anomalous decay rate of the quasinormal modes (QNMs) of a massive scalar field which was recently reported in Schwarzschild black hole backgrounds, in which the longest-lived modes are the ones with higher angular number, for a scalar field mass smaller than a critical value, while that beyond this value the behavior is inverted. We study the QNMs for various overtone numbers and they depend on a parameter $$\beta $$
which appears in the metric and characterizes the f(R) gravity. For small $$\beta $$
, i.e. small deviations from the Schwarzschild–dS black hole the anomalous behavior in the QNMs is present for the photon sphere modes, and the critical value of the mass of the scalar field depends on the parameter $$\beta $$
while for large $$\beta $$
, i.e. large deviations, the anomalous behavior and the critical mass does not appear. Also, the critical mass of the scalar field increases when the overtone number increases until the f(R) gravity parameter $$\beta $$
approaches the near extremal limit at which the critical mass of the scalar field does not depend anymore on the overtone number. The imaginary part of the quasinormal frequencies is always negative leading to a stable propagation of the scalar fields in this background.

... read more

Topics: Scalar field (60%), f(R) gravity (59%), Scalar (mathematics) (56%) ... read more

5 Citations

•••

Abstract: In this paper, we show how the quasinormal modes (QNMs) arise from the perturbations of massive scalar fields propagating in the curved background by using the artificial neural networks. To this end, we architect a special algorithm for the feedforward neural network method (FNNM) to compute the QNMs complying with the certain types of boundary conditions. To test the reliability of the method, we consider two black hole spacetimes whose QNMs are well-known: $4D$ pure de Sitter (dS) and five-dimensional Schwarzschild anti-de Sitter (AdS) black holes. Using the FNNM, the QNMs of are computed numerically. It is shown that the obtained QNMs via the FNNM are in good agreement with their former QNM results resulting from the other methods. Therefore, our method of finding the QNMs can be used for other curved spacetimes that obey the same boundary conditions.

... read more

Topics: Schwarzschild radius (52%), Black hole (51%)

2 Citations

More

60 results found

•••

B. P. Abbott^{1}, Richard J. Abbott^{1}, T. D. Abbott^{2}, Matthew Abernathy^{1} +1008 more•Institutions (96)

Abstract: On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of $1.0 \times 10^{-21}$. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1 {\sigma}. The source lies at a luminosity distance of $410^{+160}_{-180}$ Mpc corresponding to a redshift $z = 0.09^{+0.03}_{-0.04}$. In the source frame, the initial black hole masses are $36^{+5}_{-4} M_\odot$ and $29^{+4}_{-4} M_\odot$, and the final black hole mass is $62^{+4}_{-4} M_\odot$, with $3.0^{+0.5}_{-0.5} M_\odot c^2$ radiated in gravitational waves. All uncertainties define 90% credible intervals.These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

... read more

Topics: Binary black hole (60%), Black hole (58%), Primordial black hole (54%) ... read more

8,011 Citations

••

Abstract: We review in detail a number of approaches that have been adopted to try and explain the remarkable observation of our accelerating universe. In particular we discuss the arguments for and recent progress made towards understanding the nature of dark energy. We review the observational evidence for the current accelerated expansion of the universe and present a number of dark energy models in addition to the conventional cosmological constant, paying particular attention to scalar field models such as quintessence, K-essence, tachyon, phantom and dilatonic models. The importance of cosmological scaling solutions is emphasized when studying the dynamical system of scalar fields including coupled dark energy. We study the evolution of cosmological perturbations allowing us to confront them with the observation of the Cosmic Microwave Background and Large Scale Structure and demonstrate how it is possible in principle to reconstruct the equation of state of dark energy by also using Supernovae Ia observational data. We also discuss in detail the nature of tracking solutions in cosmology, particle physics and braneworld models of dark energy, the nature of possible future singularities, the effect of higher order curvature terms to avoid a Big Rip singularity, and approaches to modifying gravity which leads to a late-time accelerated expansion without recourse to a new form of dark energy.

... read more

Topics: Dark fluid (71%), Dark energy (70%), Lambda-CDM model (70%) ... read more

5,384 Citations

••

Abstract: On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160) Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

... read more

Topics: Stellar black hole (81%), Rotating black hole (77%), Binary black hole (76%) ... read more

4,375 Citations

•••

Timothy Clifton^{1}, Pedro G. Ferreira^{1}, Antonio Padilla^{2}, Constantinos Skordis^{2}•Institutions (2)

Abstract: In this review we present a thoroughly comprehensive survey of recent work on modified theories of gravity and their cosmological consequences. Amongst other things, we cover General Relativity, scalar–tensor, Einstein–aether, and Bimetric theories, as well as TeVeS, f ( R ) , general higher-order theories, Hořava–Lifschitz gravity, Galileons, Ghost Condensates, and models of extra dimensions including Kaluza–Klein, Randall–Sundrum, DGP, and higher co-dimension braneworlds. We also review attempts to construct a Parameterised Post-Friedmannian formalism, that can be used to constrain deviations from General Relativity in cosmology, and that is suitable for comparison with data on the largest scales. These subjects have been intensively studied over the past decade, largely motivated by rapid progress in the field of observational cosmology that now allows, for the first time, precision tests of fundamental physics on the scale of the observable Universe. The purpose of this review is to provide a reference tool for researchers and students in cosmology and gravitational physics, as well as a self-contained, comprehensive and up-to-date introduction to the subject as a whole.

... read more

Topics: Quantum cosmology (61%), General relativity (56%), Extra dimensions (55%) ... read more

3,018 Citations

•••

Abstract: The classical generalization of general relativity is considered as the gravitational alternative for a unified description of the early-time inflation with late-time cosmic acceleration. The structure and cosmological properties of a number of modified theories, including traditional F ( R ) and Hořava–Lifshitz F ( R ) gravity, scalar-tensor theory, string-inspired and Gauss–Bonnet theory, non-local gravity, non-minimally coupled models, and power-counting renormalizable covariant gravity are discussed. Different representations of and relations between such theories are investigated. It is shown that some versions of the above theories may be consistent with local tests and may provide a qualitatively reasonable unified description of inflation with the dark energy epoch. The cosmological reconstruction of different modified gravities is provided in great detail. It is demonstrated that eventually any given universe evolution may be reconstructed for the theories under consideration, and the explicit reconstruction is applied to an accelerating spatially flat Friedmann–Robertson–Walker (FRW) universe. Special attention is paid to Lagrange multiplier constrained and conventional F ( R ) gravities, for latter F ( R ) theory, the effective Λ CDM era and phantom divide crossing acceleration are obtained. The occurrences of the Big Rip and other finite-time future singularities in modified gravity are reviewed along with their solutions via the addition of higher-derivative gravitational invariants.

... read more

Topics: f(R) gravity (67%), General relativity (61%), Dark energy (59%) ... read more

3,009 Citations