Built-in scordatura in U-DHOST

De Felice, Antonio; Mukohyama, Shinji; Takahashi, Kazufumi

doi:10.48550/arxiv.2204.02032

Cited by 3 publications

(4 citation statements)

References 41 publications

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“…In fact, we expect that a similar story to the DHOST analysis should play out for perturbations, so that a degeneracy condition between coefficient functions of higher-derivative operators can be imposed, reducing the equation of motion to second order. Furthermore, it is possible for higher derivative operators to serve as "Scordatura terms" [55][56][57], which contribute to a non-vanishing dispersion relation in such a way as to solve the strong coupling problem for some solutions.…”

Section: Discussionmentioning

confidence: 99%

Stability of Hairy Black Holes in Shift-Symmetric Scalar-Tensor Theories via the Effective Field Theory Approach

Khoury¹,

Noumi²,

Trodden³

et al. 2022

Preprint

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Shift-symmetric Horndeski theories admit an interesting class of Schwarzschild-de Sitter black hole solutions exhibiting time-dependent scalar hair. The properties of these solutions may be studied via a bottom-up effective field theory (EFT) based on the background symmetries. This is in part possible by making use of a convenient coordinate choice -Lemaître-type coordinates -in which the profile of the Horndeski scalar field is linear in the relevant time coordinate. We construct this EFT, and use it to understand the stability of hairy black holes in shift-symmetric Horndeski theories, providing a set of constraints that the otherwise-free functions appearing in the Horndeski Lagrangian must satisfy in order to admit stable black hole solutions. The EFT is analyzed in the decoupling limit to understand potential sources of instability. We also perform a complete analysis of the EFT with odd-parity linear perturbations around general spherically symmetric space-time.

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Section: Discussionmentioning

confidence: 99%

Stability of Hairy Black Holes in Shift-Symmetric Scalar-Tensor Theories via the Effective Field Theory Approach

Khoury¹,

Noumi²,

Trodden³

et al. 2022

Preprint

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“…The polar sector, which we do not consider in the present work, is however pathological, as stressed in[12]. A possible way out involves a slight detuning of the degeneracy conditions[53], which for example manifests itself in U-DHOST theories[54], as discussed in[55].…”

mentioning

confidence: 87%

On the effective metric of axial black hole perturbations in DHOST gravity

Langlois

Noui

Roussille

2022

J. Cosmol. Astropart. Phys.

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We study axial (or odd-parity) perturbations about static and spherically symmetric hairy black hole (BH) solutions in shift-symmetric DHOST (Degenerate Higher-Order Scalar-Tensor) theories. We first extend to the family of DHOST theories the first-order formulation that we recently developed for Horndeski theories. Remarkably, we find that the dynamics of DHOST axial perturbations is equivalent to that of axial perturbations in general relativity (GR) evolving in a, distinct, effective metric. In the particular case of quadratic DHOST theories, this effective metric is derived from the background BH metric via a disformal transformation. We illustrate our general study with three examples of BH solutions. In some so-called stealth solutions, the effective metric is Schwarzschild with a shifted horizon. We also give an example of BH solution for which the effective metric is associated with a naked singularity.

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“…Within the general scalar-tensor extensions of GR aiming to explain dark energy, known as DHOST theories, the weakfield limit of the theory predicts that the hydrostatic equilibrium of massive objects is modified through a new fifth-force term (Kobayashi et al 2015;Crisostomi & Koyama 2018;Dima & Vernizzi 2018;Koyama & Sakstein 2015) as…”

Section: Introductionmentioning

confidence: 99%

“…Earlier works constraining the fifth-force coupling Y were carried out in the context of white dwarfs (Jain et al 2016;Saltas et al 2018), red and brown dwarfs (Sakstein 2015a,b;Kozak et al 2022), main-sequence stars , relativistic compact objects (Babichev et al 2016), galaxy clusters (Sakstein et al 2016;Pizzuti et al 2019Pizzuti et al , 2021Laudato et al 2022;Haridasu et al 2021), the Hulse-Taylor pulsar (Dima & Vernizzi 2018), gravitational waves (Creminelli & Vernizzi 2017;Ezquiaga & Zumalacárregui 2017;Baker et al 2017;Sakstein & Jain 2017;Creminelli et al 2018), and the Solar System (Crisostomi et al 2019) 1 . All constraints from stellar scales have thus far imposed Y < O(0.1) at 2σ.…”

Section: Introductionmentioning

confidence: 99%

Searching for dark energy with the Sun

Saltas

Christensen‐Dalsgaard

2022

A&A

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General extensions of general relativity (GR) based on bona fide degrees of freedom predict a fifth force which operates within massive objects, opening up an exciting opportunity to perform precision tests of gravity at stellar scales. Here, focussing on general scalar-tensor theories for dark energy, we utilise the Sun as our laboratory and search for imprints of the fifth-force effect on the solar equilibrium structure. With analytic results and numerical simulations, we explain how the different solar regions offer powerful ways to test gravity. Accounting for the delicate interplay between the fifth force and solar microphysics such as opacity, diffusion, equation of state, and metallicity, we demonstrate that the fifth force still leaves a sharp signature on the solar sound speed, in a region where simple estimates of input physics uncertainties become negligible. For general scalar-field extensions of GR, known as (U-)DHOST, based solely on the observational helioseismic errors, our analysis at the equilibrium level allows us to place an approximate constraint on the fifth-force coupling strength of −10 −3 Y 5 • 10 −4 at 2σ. This result improves previous stellar constraints by ∼ 3 orders of magnitude, and should be confirmed and improved by future helioseismic inversions in modified gravity, combined with an elaborate accounting of theoretical uncertainties. Our analysis can be applied to a wide set of theories beyond GR, and also paves the way for helioseismic analyses in this context. In this regard, we discuss how the solar radiative and convective zone can be employed as promising laboratories to test generic theories of gravity.

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Built-in scordatura in U-DHOST

Cited by 3 publications

References 41 publications

Stability of Hairy Black Holes in Shift-Symmetric Scalar-Tensor Theories via the Effective Field Theory Approach

Stability of Hairy Black Holes in Shift-Symmetric Scalar-Tensor Theories via the Effective Field Theory Approach

On the effective metric of axial black hole perturbations in DHOST gravity

Searching for dark energy with the Sun

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