Onset of spontaneous scalarization in generalized scalar-tensor theories

Ventagli, Giulia; Lehébel, Antoine; Sotiriou, Thomas P.

doi:10.1103/physrevd.102.024050

Cited by 41 publications

(37 citation statements)

References 34 publications

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“…Compact stars can scalarize for η < 0 [33] and hence yield constraints. However, this effect could easily be quenched by adding a coupling between the scalar field and the Ricci scalar [41,60]. The latter might be necessary to get a sensible cosmology [61], and would have no effect for black holes, thus leaving our analysis unaffected.…”

Section: Resultsmentioning

confidence: 99%

Spin-Induced Black Hole Spontaneous Scalarization

et al. 2020

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We study scalar fields in a black hole background and show that, when the scalar is suitably coupled to curvature, rapid rotation can induce a tachyonic instability. This instability, which is the hallmark of spontaneous scalarization in the linearized regime, is expected to be quenched by nonlinearities and endow the black hole with scalar hair. Hence, our results demonstrate the existence of a broad class of theories that share the same stationary black hole solutions with general relativity at low spins, but which exhibit black hole hair at sufficiently high spins (a/M 0.5). This result has clear implications for tests of general relativity and the nature of black holes with gravitational and electromagnetic observations.

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Section: Resultsmentioning

confidence: 99%

Spin-Induced Black Hole Spontaneous Scalarization

et al. 2020

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“…The fact that the onset of scalarization is captured in linear theory allows one to identify all possible couplings to curvature that can lead to scalarization [31] and simplifies the investigation of the relevant thresholds [32]. It also makes it straightforward to generalize the mechanism to nongravitational couplings (see, e.g., [33,34]).…”

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confidence: 99%

Spin-Induced Scalarized Black Holes

et al. 2021

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It was recently shown that a scalar field suitably coupled to the Gauss-Bonnet invariant G can undergo a spin-induced linear tachyonic instability near a Kerr black hole. This instability appears only once the dimensionless spin j is sufficiently large, that is, j 0.5. A tachyonic instability is the hallmark of spontaneous scalarization. Focusing, for illustrative purposes, on a class of theories that do exhibit this instability, we show that stationary, rotating black hole solutions do indeed have scalar hair once the spin-induced instability threshold is exceeded, while black holes that lie below the threshold are described by the Kerr solution. Our results provide strong support for spin-induced black hole scalarization.

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“…Originally, spontaneous scalarization has been identified for spherically symmetric NS models in a class of massless ST theories sometimes refered to as Bergmann-Wagoner [22,23] theories; these complement the metric sector of GR with a single scalar field, are governed by second-order covariant field Equations at most linear in second and quadratic in first derivatives, and obey the weak equivalence principle. The phenomenon has by now been demonstrated to occur over a wide range of configurations and also in other theoretical frameworks [24,25]. Analogous phenomena occur in many scenarios involving fields non-minimally coupled to a spacetime metric.…”

Section: Introductionmentioning

confidence: 72%

Structure of Neutron Stars in Massive Scalar-Tensor Gravity

et al. 2020

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We compute families of spherically symmetric neutron-star models in two-derivative scalar-tensor theories of gravity with a massive scalar field. The numerical approach we present allows us to compute the resulting spacetimes out to infinite radius using a relaxation algorithm on a compactified grid. We discuss the structure of the weakly and strongly scalarized branches of neutron-star models thus obtained and their dependence on the linear and quadratic coupling parameters α0, β0 between the scalar and tensor sectors of the theory, as well as the scalar mass μ. For highly negative values of β0, we encounter configurations resembling a “gravitational atom”, consisting of a highly compact baryon star surrounded by a scalar cloud. A stability analysis based on binding-energy calculations suggests that these configurations are unstable and we expect them to migrate to models with radially decreasing baryon density and scalar field strength.

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Onset of spontaneous scalarization in generalized scalar-tensor theories

Cited by 41 publications

References 34 publications

Spin-Induced Black Hole Spontaneous Scalarization

Spin-Induced Black Hole Spontaneous Scalarization

Spin-Induced Scalarized Black Holes

Structure of Neutron Stars in Massive Scalar-Tensor Gravity

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