Cosmic black-hole hair growth and quasar OJ287

Horbatsch, Michael; Burgess, C.P.

doi:10.1088/1475-7516/2012/05/010

Cited by 83 publications

(97 citation statements)

References 113 publications

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“…Another possibility is a distribution of cosmological matter that can support a time-varying scalar field at infinity. This possibility has been called "Jacobson's miracle hair-growth formula" for black holes, based on work by Jacobson [58,59]. Whether it is possible to incorporate such ideas into our approach is a subject for future work.…”

Section: Binary Black Holesmentioning

confidence: 99%

Compact binary systems in scalar-tensor gravity: Equations of motion to 2.5 post-Newtonian order

2013

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We calculate the explicit equations of motion for non-spinning compact objects to 2.5 post- Newtonian order, or O(v/c) 5 beyond Newtonian gravity, in a general class of scalar-tensor theories of gravity. We use the formalism of the Direct Integration of the Relaxed Einstein Equations (DIRE), adapted to scalar-tensor theory, coupled with an approach pioneered by Eardley for incorporating the internal gravity of compact, self-gravitating bodies. For the conservative part of the motion, we obtain the two-body Lagrangian and conserved energy and momentum through second post-Newtonian order. We find the 1.5 post-Newtonian and 2.5 post-Newtonian contributions to gravitational radiation reaction, the former corresponding to the effects of dipole gravitational radiation, and verify that the resulting energy loss agrees with earlier calculations of the energy flux. For binary black holes we show that the motion through 2.5 post-Newtonian order is observationally identical to that predicted by general relativity. For mixed black-hole neutron-star binary systems, the motion is identical to that in general relativity through the first post-Newtonian order, but deviates from general relativity beginning at 1.5 post-Newtonian order, in part through the onset of dipole gravitational radiation. But through 2.5 post-Newtonian order, those deviations in the motion of a mixed system are governed by a single parameter dependent only upon the coupling constant ω0 and the structure of the neutron star, and are formally the same for a general class of scalar-tensor theories as they are for pure Brans-Dicke theory.

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Section: Binary Black Holesmentioning

confidence: 99%

Compact binary systems in scalar-tensor gravity: Equations of motion to 2.5 post-Newtonian order

2013

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“…For nontrivial time-dependent boundary conditions or background scalar fields, however, nontrivial results show up. These boundary conditions could mimic cosmological scenarios or dark matter profiles in galaxies [434, 92]. Reference [92] modelled a BH binary evolving nonlinearly in a constant-gradient scalar field.…”

Section: Applications Of Numerical Relativitymentioning

confidence: 99%

Exploring New Physics Frontiers Through Numerical Relativity

et al. 2015

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The demand to obtain answers to highly complex problems within strong-field gravity has been met with significant progress in the numerical solution of Einstein’s equations — along with some spectacular results — in various setups.We review techniques for solving Einstein’s equations in generic spacetimes, focusing on fully nonlinear evolutions but also on how to benchmark those results with perturbative approaches. The results address problems in high-energy physics, holography, mathematical physics, fundamental physics, astrophysics and cosmology.

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“…In standard scalar-tensor theories, both cases lead to generation of scalar hair [21][22][23][24][25][26].…”

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confidence: 99%

Black Hole Hair in Generalized Scalar-Tensor Gravity

2014

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The most general action for a scalar field coupled to gravity that leads to second order field equations for both the metric and the scalar -Horndeski's theory -is considered, with the extra assumption that the scalar satisfies shift symmetry. We show that in such theories the scalar field is forced to have a nontrivial configuration in black hole spacetimes, unless one carefully tunes away a linear coupling with the Gauss-Bonnet invariant. Hence, black holes for generic theories in this class will have hair. This contradicts a recent no-hair theorem, which seems to have overlooked the presence of this coupling.PACS numbers: 04.70. Bw, 04.50.Kd In general relativity, black hole spacetimes are described by the Kerr metric, so long as they are stationary, asymptotically flat, and devoid of any matter in their surroundings [1]. Stationarity is a reasonable assumption for black holes that are thought to be quiescent as endpoints of gravitational collapse. Astrophysical black holes are certainly not asymptotically flat, but one can invoke separation of scales in order to argue that the cosmological background should not seriously affect local physics and hence the structure of black holes. Finally, black holes can also carry an electromagnetic charge in the presence of an electromagnetic field. It has been conjectured that they cannot carry any other charges, which are colloquially referred to as hair [2][27]. The no-hair conjecture was inspired by the uniqueness theorems for black hole solutions in general relativity [4][5][6][7].Hawking has proven that black holes cannot carry scalar charge, provided that the scalar couples to the metric minimally or as described by Brans-Dicke theory [8]. This result has been generalised to standard scalar-tensor theories [9] (see also earlier work by Bekenstein with the extra assumption of spherical symmetry [10,11]).All of these proofs actually demonstrate that the scalar has to be constant in a black hole spacetime, which is a stronger statement. Indeed, in principle, the scalar could have a nontrivial configuration without the black hole carrying an extra (independent) charge. This is sometime referred to as "hair of the second kind". The distinction is important if one is interested in the number of parameters that fully characterise the spacetime. But, a nontrivial configuration of the scalar is usually enough to imply that the black hole spacetime will not be a solution to Einstein's equations in vacuum, and hence it differs from the black holes of general relativity.The known proofs do not apply to theories with more general coupling between the metric and the scalar, or derivative self-interactions of the scalar. Hence, they do not cover the most general scalar-tensor theory that leads to second-order field equations, known as Horndeski theory [12]. Restricting attention to theories with second order field equations is justified, as higher order derivative models are generically plagued by the Ostrogradski instability [13]. Models that belong to this class have lately ...

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Cosmic black-hole hair growth and quasar OJ287

Cited by 83 publications

References 113 publications

Compact binary systems in scalar-tensor gravity: Equations of motion to 2.5 post-Newtonian order

Compact binary systems in scalar-tensor gravity: Equations of motion to 2.5 post-Newtonian order

Exploring New Physics Frontiers Through Numerical Relativity

Black Hole Hair in Generalized Scalar-Tensor Gravity

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