Galileon accretion

Babichev, Eugeny

doi:10.1103/physrevd.83.024008

Cited by 35 publications

(46 citation statements)

References 32 publications

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“…Indeed, in [30], a process of accretion of Galileon onto a static spherically symmetric black hole was studied, where the backreaction of the scalar field on the black hole was neglected -exactly the situation we consider in this subsection, the test approximation. The key difference of the accreting solution in [30] from our solution (4.12) is an integration constant, which vanishes for the solution presented here. As we discussed above, the solution in the test field approximation follows from the (tr) Einstein equation (4.1), which is equivalent to the equation J r = 0.…”

Section: Test Field Limitmentioning

confidence: 99%

Black holes in a cubic Galileon universe

Babichev

Charmousis

Lehébel

et al. 2016

J. Cosmol. Astropart. Phys.

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100

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Abstract. We find and study the properties of black hole solutions for a subclass of Horndeski theory including the cubic Galileon term. The theory under study has shift symmetry but not reflection symmetry for the scalar field. The Galileon is assumed to have linear time dependence characterized by a velocity parameter. We give analytic 3-dimensional solutions that are akin to the BTZ solutions but with a non-trivial scalar field that modifies the effective cosmological constant. We then study the 4-dimensional asymptotically flat and de Sitter solutions. The latter present three different branches according to their effective cosmological constant. For two of these branches, we find families of black hole solutions, parametrized by the velocity of the scalar field. These spherically symmetric solutions, obtained numerically, are different from GR solutions close to the black hole event horizon, while they have the same de-Sitter asymptotic behavior. The velocity parameter represents black hole primary hair.arXiv:1605.07438v2 [gr-qc]

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Section: Test Field Limitmentioning

confidence: 99%

Black holes in a cubic Galileon universe

Babichev

Charmousis

Lehébel

et al. 2016

J. Cosmol. Astropart. Phys.

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100

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“…The ansatz (6) has been used in a similar context for the study of the Galileon accretion [15] and the effects of cosmologically evolving scalar field on the variation of the Newton constant [10]. Actually, since ' 0 ¼ 0 (where a prime denotes a radial derivative), the notation will not be useful in the following, and we can thus write Eq.…”

Section: Background Solutionmentioning

confidence: 99%

“…The crucial information brought by Eq. (15) is that the spin-2 graviton is never a ghost, and that the effective metric (16) should be of signature À þ þþ for the scalar perturbation to carry positive energy and have a well-posed Cauchy problem. We shall perform this analysis in Secs.…”

Section: Perturbationsmentioning

confidence: 99%

Time-dependent spherically symmetric covariant Galileons

Babichev

Esposito-Farèse

2013

Phys. Rev. D

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We study spherically symmetric solutions of the cubic covariant Galileon model in curved spacetime in presence of a matter source, in the test scalar field approximation. We show that a cosmological time evolution of the Galileon field gives rise to an induced matter-scalar coupling, due to the Galileon-graviton kinetic braiding, therefore the solution for the Galileon field is non trivial even if the bare matter-scalar coupling constant is set to zero. The local solution crucially depends on the asymptotic boundary conditions, and in particular, Minkowski and de Sitter asymptotics correspond to different branches of the solution. We study the stability of these solutions, namely, the well-posedness of the Cauchy problem and the positivity of energy for scalar and tensor perturbations, by diagonalizing the kinetic terms of the spin-2 and spin-0 degrees of freedom. In addition, we find that in presence of a cosmological time evolution of the Galileon field, its kinetic mixing with the graviton leads to a friction force, resulting to efficient damping of scalar perturbations within matter.Comment: 20 pages, no figure, RevTeX4 format; v2: minor changes reflecting the published version in PR

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“…(28) for w ¼ 0. Equation (37) can be also derived from the spatial part of the Bianchi identities. It follows that…”

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confidence: 99%

Matter perturbations in Galileon cosmology

2011

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We study the evolution of matter density perturbations in Galileon cosmology where the late-time cosmic acceleration can be realized by a field kinetic energy. We obtain full perturbation equations at linear order in the presence of five covariant Lagrangians ${cal L}_i$ ($i=1,...,5$) satisfying a Galilean symmetry in the flat space-time. The equations for a matter perturbation as well as an effective gravitational potential are derived under a quasi-static approximation on sub-horizon scales. This approximation can reproduce full numerical solutions with high accuracy for the wavelengths relevant to large-scale structures. For the model parameters constrained by the background expansion history of the Universe the growth rate of matter perturbations is larger than that in the LCDM model, with the growth index $gamma$ today typically smaller than 0.4. We also find that, even on very large scales associated with the Integrated-Sachs-Wolfe (ISW) effect in Cosmic Microwave Background (CMB) temperature anisotropies, the effective gravitational potential exhibits a temporal growth during the transition from the matter era to the epoch of cosmic acceleration. These properties are useful to distinguish the Galileon model from the LCDM in future high-precision observations.Comment: 17 pages, 5 figure

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Galileon accretion

Cited by 35 publications

References 32 publications

Black holes in a cubic Galileon universe

Black holes in a cubic Galileon universe

Time-dependent spherically symmetric covariant Galileons

Matter perturbations in Galileon cosmology

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