Obtaining Precision Constraints on Modified Gravity with Helioseismology

Saltas, Ippocratis D.; Lopes, Ilídio

doi:10.1103/physrevlett.123.091103

Cited by 51 publications

(37 citation statements)

References 57 publications

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“…In DHOST theories, if the scalar field has cosmological time-dependence, the effects of the fifth force can be enhanced inside astrophysical bodies; constraints in terms of stellar dynamics have been obtained in Refs. [9,13,15,52].…”

Section: The Dhost Theoriesmentioning

confidence: 99%

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Black holes with a nonconstant kinetic term in degenerate higher-order scalar tensor theories

Minamitsuji

Edholm

2020

Phys. Rev. D

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We investigate static and spherically symmetric black hole (BH) solutions in shift-symmetric quadratic-order degenerate higher-order scalar-tensor (DHOST) theories. We allow a nonconstant kinetic term X = g µν ∂µφ∂ν φ for the scalar field φ and assume that φ is, like the spacetime, a pure function of the radial coordinate r, namely φ = φ(r). First, we find analytic static and spherically symmetric vacuum solutions in the so-called Class Ia DHOST theories, which include the quartic Horndeski theories as a subclass. We consider several explicit models in this class and apply our scheme to find the exact vacuum BH solutions. BH solutions obtained in our analysis are neither Schwarzschild or Schwarzschild (anti-) de Sitter. We show that a part of the BH solutions obtained in our analysis are free of ghost and Laplacian instabilities and are also mode stable against the oddparity perturbations. Finally, we argue the case that the scalar field has a linear time dependence φ = qt + ψ(r) and show several simple examples of nontrivial BH solutions with a nonconstant kinetic term obtained analytically and numerically. I. INTRODUCTIONScalar-tensor theories have provided the unified mathematical description of modified gravity theories [1]. In classic scalar-tensor theories, whose Lagrangian density depends on the metric g µν , the scalar field φ, and its first-order derivative φ µ := ∇ µ φ, L = L(g µν , φ, φ µ ), the Euler-Lagrange (EL) equations are given by the second-order differential equations. However, the Lagrangian density of modern scalar-tensor theories may also contain the second-order derivatives of the scalar field φ µν := ∇ µ ∇ ν φ. Although generically the EL equations in such theories contain higher derivative terms, the appearance of Ostrogradsky ghosts [2] can be avoided using certain degeneracy conditions [3]. Degenerate higher-order scalar-tensor (DHOST) theories [4-9] (see also [10,11]) provide the most general framework of scalar-tensor theories which are free from Ostrogradsky instabilities [2], and hence the system contains only three degrees of freedom (DOFs), namely, two tensorial and one scalar polarizations (See § II for details). Applications of DHOST theories to cosmological and astrophysical problems have been investigated in Refs. [9,[12][13][14][15].The application of modern scalar-tensor theories to BH physics has attracted great interest. Besides the Schwarzschild or Kerr solutions in General Relativity (GR) with or without a constant scalar field [16,17], i.e. GR BH solutions, they also allow BH solutions which are absent in GR. A typical nontrivial BH solution is the stealth Schwarzschild solution [18,19] obtained in shift-symmetric Horndeski theories with the assumptions of a linearly time-dependent scalar field φ = qt + ψ(r) and a constant kinetic term X = const, where t and r are the time and radial coordinates of the static and spherically symmetric spacetime and X := g µν φ µ φ ν represents the canonical kinetic term of the scalar field. In stealth solutions, the spacetime geometry ...

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Section: The Dhost Theoriesmentioning

confidence: 99%

“…Applications of DHOST theories to cosmological and astrophysical problems have been investigated in Refs. [9,[12][13][14][15].The application of modern scalar-tensor theories to BH physics has attracted great interest. Besides the Schwarzschild or Kerr solutions in General Relativity (GR) with or without a constant scalar field [16,17], i.e.…”

mentioning

confidence: 99%

Black holes with a nonconstant kinetic term in degenerate higher-order scalar tensor theories

Minamitsuji

Edholm

2020

Phys. Rev. D

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“…An interesting development of the present work is to extend the study of radial perturbations-explored here with focus on stability issues-to the stable case, describing NS oscillations. In the Newtonian context, it was recently suggested [43] that helioseismology may be a good probe for fifth force effects. In the relativistic scenario, it was shown [28] that, in some scalar-tensor theories that exhibit the scalarization effect, NS oscillation frequencies can differ significantly from GR even when structural properties are similar, due to the presence of new families of modes (see also Ref.…”

Section: Final Discussionmentioning

confidence: 99%

Highly compact neutron stars and screening mechanisms. I. Equilibrium and stability

de Aguiar,

Mendes

2020

Preprint

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Modified theories of gravity that offer viable models for dark energy often rely on mechanisms that screen their effects in high density environments. From this perspective, it would appear that, once solar system constraints are satisfied, these theories would predict a trivial phenomenology for (much denser) neutron stars. In this work we explore the fact that in scalar-tensor theories the scalar degree of freedom does not couple to the mass density alone, but to the trace of the energy-momentum tensor-which can increase and eventually change sign as density and pressure build up in the core of neutron stars-, and investigate whether there could be a partial unscreening of the scalar field inside the most compact stars found in Nature. For this purpose, we construct neutron star solutions with realistic equations of state in theories with screening mechanisms and study their stability under radial perturbations. In particular, we find that stable solutions with a unscreened core can exist in chameleon models, while for the environmentally-dependent dilaton model a wealth of new, scalarized equilibrium solutions are found, some of which can be stable.

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“…Let us just mention, as a concluding remark to that point, that so far only helioseismic data has been used to constrain modified gravity models [130,131].…”

Section: • Exoplanets Propertiesmentioning

confidence: 98%

Metric-affine gravity effects on terrestrial (exo-)planets profiles

Kozak,

Wojnar

2021

Preprint

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Mass-radius relations of homogeneous cold spheres are obtained for six solid materials commonly found in terrestrial planets. An additional degeneracy in the (exo-)planets' profiles is discussed together with their properties concluded from our findings in the framework of Palatini f (R) gravity. Moreover, a new test of gravity has been proposed: The results presented here will allow to test and to constrain models of gravity by the use of seismic data acquired from earthquakes and marsquakes.

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Obtaining Precision Constraints on Modified Gravity with Helioseismology

Cited by 51 publications

References 57 publications

Black holes with a nonconstant kinetic term in degenerate higher-order scalar tensor theories

Black holes with a nonconstant kinetic term in degenerate higher-order scalar tensor theories

Highly compact neutron stars and screening mechanisms. I. Equilibrium and stability

Metric-affine gravity effects on terrestrial (exo-)planets profiles

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