Odd-parity stability of black holes in Einstein-Aether gravity

Tsujikawa, Shinji; Zhang, Chao; Zhao, Xiang; Wang, Anzhong

doi:10.48550/arxiv.2107.08061

Cited by 3 publications

(3 citation statements)

References 54 publications

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“…For perturbations respecting the spherical symmetry the dynamical simulations of [13] show certain black holes are stable since they form the end state of collapse, although these are not for phenomenologically allowed parameters. However, the recent [54] reports some static spherically symmetric solutions are unstable to perturbations that break the spherical symmetry. Constructing dynamical linearized Einstein-aether perturbations about our numerical stationary solutions seems like a difficult task.…”

Section: Discussionmentioning

confidence: 99%

Rotating black holes in Einstein-aether theory

Adam

Figueras

Jacobson

et al. 2022

Class. Quantum Grav.

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We introduce new methods to numerically construct for the ﬁrst time stationary axisymmetric black hole solutions in Einstein-aether theory and study their properties. The key technical challenge is to impose regularity at the spin-2, 1, and 0 wave mode horizons. Interestingly we ﬁnd the metric horizon, and various wave mode horizons, are not Killing horizons, having null generators to which no linear combination of Killing vectors is tangent, and which spiral from pole to equator or vice versa. Existing phenomenological constraints result in two regions of coupling parameters where the theory is viable and some couplings are large; region I with a large twist coupling and region II with also a (somewhat) large expansion coupling. Currently these constraints do not include tests from strong ﬁeld dynamics, such as observations of black holes and their mergers. Given the large aether coupling(s) one might expect such dynamics to deviate signiﬁcantly from general relativity, and hence to further constrain the theory. Here we argue this is not the case, since for these parameter regions solutions exist where the aether is “painted” onto a metric background that is very close to that of general relativity. This painting for region I is approximately independent of the large twist coupling, and for region II is also approximately independent of the large expansion coupling and normal to a maximal foliation of the spacetime. We support this picture analytically for weak ﬁelds, and numerically for rotating black hole solutions, which closely approximate the Kerr metric.

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Section: Discussionmentioning

confidence: 99%

Rotating black holes in Einstein-aether theory

Adam

Figueras

Jacobson

et al. 2022

Class. Quantum Grav.

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“…These values of c 2 Ω± were not derived in the literature even in the absence of matter. Given that there are some modified gravity (vector-tensor) theories in which hairy BH solutions are subject to Laplacian instabilities along the angular direction [90,93], our general expressions of c 2 Ω± will be useful to select stable NS and BH solutions in Horndeski theories. In Sec.…”

Section: Discussionmentioning

confidence: 99%

Relativistic star perturbations in Horndeski theories with a gauge-ready formulation

Kase,

Tsujikawa

2021

Preprint

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We present a general framework for studying the relativistic star perturbations on a static and spherically symmetric background in full Horndeski theories. We take a perfect fluid into account as a form of the Schutz-Sorkin action. Our formulation is sufficiently versatile in that the secondorder actions of perturbations in odd-and even-parity sectors are derived without choosing particular gauge conditions, so they can used for any convenient gauges at hand. The odd-parity sector contains one dynamical gravitational degree of freedom coupled to a time-independent four velocity of the fluid. In the even-parity sector there are three dynamical perturbations associated with gravity, scalar field, and matter sectors, whose equations of motion are decoupled from other nondynamical perturbations. For high radial and angular momentum modes, we obtain the propagation speeds of all dynamical perturbations and show that the perfect fluid in the even-parity sector has a standard sound speed affected by neither gravity nor the scalar field. Our general stability conditions and perturbation equations of motion can be directly applied to the stabilities of neutron stars and black holes as well as the calculations of their quasi-normal frequencies.

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“…However, possible violations of these two symmetries may arise in theories that try to unify quantum physics with gravity. Because of this, various modified theories of gravity have been proposed to explore the nature of parity and Lorentz violations in gravity, to mention a few, including the Chern-Simons modified gravity [28,29], the symmetric teleparallel equivalence JCAP07(2024)005 of GR theory [30,31], Horava-Lifshitz theories of quantum gravity [32][33][34][35][36][37][38], chiral scalar-tensor theory [39], the Nieh-Yan teleparallel modified gravity [40][41][42], parity-violating scalar-tensor theory in teleparallel gravity [43], parity violation induced by couplings between dual Reimann tensor and Kalb-Ramond two-form field [44], the linearized gravity in standard model extension [45,46], Einstein-AEther theories [47][48][49][50][51][52][53][54], and the spatial covariant gravities [55][56][57][58][59][60], etc.…”

Section: Introductionmentioning

confidence: 99%

Power spectra and circular polarization of primordial gravitational waves with parity and Lorentz violations

Li,

Zhu,

Zhao

et al. 2024

J. Cosmol. Astropart. Phys.

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The violations of parity and Lorentz symmetries in gravity can change the propagating properties of gravitational waves (GWs) in the cosmological background, which can arise from a large number of parity- and Lorentz-violating theories. In this paper, through a systematic parametrization for characterizing possible derivations from the standard GW propagation in general relativity, we study both the parity- and Lorentz-violating effects on the power spectra and the polarization of the primordial gravitational waves (PGWs) during the slow-roll inflation. To this end, we calculate explicitly the power spectrum and the corresponding circular polarization of the PGWs analytically by using the uniform asymptotic approximation. It is shown that the new contributions to power spectra contain two parts, one from the parity-violating terms and the other from the Lorentz-violating terms. While the Lorentz-violating terms can only affect the overall amplitudes of PGWs, the parity-violating terms induce nonzero circular polarization of PGWs, i.e., the left-hand and right-hand polarization modes of GWs have different amplitudes.

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Odd-parity stability of black holes in Einstein-Aether gravity

Cited by 3 publications

References 54 publications

Rotating black holes in Einstein-aether theory

Rotating black holes in Einstein-aether theory

Relativistic star perturbations in Horndeski theories with a gauge-ready formulation

Power spectra and circular polarization of primordial gravitational waves with parity and Lorentz violations

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