Slowly Rotating Anisotropic Neutron Stars in General Relativity and Scalar-Tensor Theory

Silva, Hector O.; Macedo, Caio F. B.; Berti, Emanuele; Crispino, Luís C. B.

doi:10.48550/arxiv.1411.6286

Cited by 23 publications

(33 citation statements)

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“…2, where we show the mass-radius relation for different values of Q ∞ and η = ±1. Note that a similar effect was found for anisotropic stars in [27]. From Fig.…”

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confidence: 82%

Neutron stars in general second order scalar-tensor theory: The case of nonminimal derivative coupling

2015

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We consider the sector of Horndeski's gravity characterized by the coupling between the kinetic scalar field term and the Einstein tensor. We numerically construct neutron star configurations where the external geometry is identical to the Schwarzschild metric but the interior structure is considerably different from standard general relativity. We constrain the only parameter of this model from the requirement that compact configurations exist, and we argue that solutions less compact than neutron stars, such as white dwarfs, are also supported. Therefore, our model provides an explicit modification of general relativity that is astrophysically viable and does not conflict with Solar System tests.

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“…2, where we show the mass-radius relation for different values of Q ∞ and η = ±1. Note that a similar effect was found for anisotropic stars in [27]. From Fig.…”

supporting

confidence: 82%

Neutron stars in general second order scalar-tensor theory: The case of nonminimal derivative coupling

2015

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“…These two expressions can be matched if 2rσ = ρmπ i f i (r). The compactness of anisotropic stars is known to decrease (increase) when σ increases (decreases) [61]. This conclusion is in good qualitative agreement with the results shown in the left panel of Fig.…”

Section: Discussionsupporting

confidence: 90%

Post-Tolman-Oppenheimer-Volkoff formalism for relativistic stars

et al. 2015

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Besides their astrophysical interest, compact stars also provide an arena for understanding the properties of theories of gravity that differ from Einstein's general relativity. Numerous studies have shown that different modified theories of gravity can modify the bulk properties (such as mass and radius) of neutron stars for given assumptions on the microphysics. What is not usually stressed though is the strong degeneracy in the predictions of these theories for the stellar mass and radius. Motivated by this observation, in this paper we take an alternative route and construct a stellar structure formalism which, without adhering to any particular theory of gravity, describes in a simple parametrized form the departure from compact stars in general relativity. This "post-TOV" formalism for spherical static stars is inspired by the well-known parametrized post-Newtonian theory, extended to second post-Newtonian order by adding suitable correction terms to the fully relativistic Tolman-Oppenheimer-Volkoff (TOV) equations. We show how neutron star properties are modified within our formalism, paying special attention to the effect of each correction term. We also show that the formalism is equivalent to general relativity with an "effective" (gravity-modified) equation of state.

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“…For a marginally allowed β 0 , nonrotating scalarized NSs would not differ considerably from the GR solutions, whereas rapid rotation can produce significant deviations that can potentially set even stronger astrophysical constraints on scalar-tensor theories [122,123]. Other proposed mechanisms that can amplify the effects of scalarization include anisotropy [539] and "dynamical scalarization" for merging NSs in scalar-tensor theories, that will be discussed in Section 5 [540][541][542][543]. In the last stages before merger the rotational frequencies of each NS may approach the Kepler limit.…”

Section: Scalar-tensor Theoriesmentioning

confidence: 99%

Testing General Relativity with Present and Future Astrophysical Observations

Berti,

Barausse,

Cardoso

et al. 2015

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One century after its formulation, Einstein's general relativity has made remarkable predictions and turned out to be compatible with all experimental tests. Most of these tests probe the theory in the weak-field regime, and there are theoretical and experimental reasons to believe that general relativity should be modified when gravitational fields are strong and spacetime curvature is large. The best astrophysical laboratories to probe strong-field gravity are black holes and neutron stars, whether isolated or in binary systems. We review the motivations to consider extensions of general relativity. We present a (necessarily incomplete) catalog of modified theories of gravity for which strong-field predictions have been computed and contrasted to Einstein's theory, and we summarize our current understanding of the structure and dynamics of compact objects in these theories. We discuss current bounds on modified gravity from binary pulsar and cosmological observations, and we highlight the potential of future gravitational wave measurements to inform us on the behavior of gravity in the strong-field regime.

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Slowly Rotating Anisotropic Neutron Stars in General Relativity and Scalar-Tensor Theory

Cited by 23 publications

References 0 publications

Neutron stars in general second order scalar-tensor theory: The case of nonminimal derivative coupling

Neutron stars in general second order scalar-tensor theory: The case of nonminimal derivative coupling

Post-Tolman-Oppenheimer-Volkoff formalism for relativistic stars

Testing General Relativity with Present and Future Astrophysical Observations

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