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

Recently, the Effective Field Theory (EFT) of perturbations on an arbitrary background metric with a timelike scalar profile was formulated in the context of scalar-tensor theories. Here, we generalize the dictionary between the coefficients in the EFT action and those in covariant theories to accommodate shift- and reflection-symmetric quadratic higher-order scalar-tensor theories, including DHOST as well as U-DHOST. We then use the EFT action to study the dynamics of odd-parity perturbations on a static and spherically symmetric black hole background with a timelike scalar profile. Finally, we obtain the generalized Regge-Wheeler equation that can be used, e.g., to determine the spectrum of quasinormal modes and tidal Love numbers.

Section: Discussionsupporting

confidence: 58%

Generalized Regge-Wheeler equation from Effective Field Theory of black hole perturbations with a timelike scalar profile

Mukohyama

Takahashi

Yingcharoenrat

2022

“…In particular, perturbations and quasi-normal modes of static and spherically symmetric black holes and neutron stars in Horndeski theory have been intensively studied in refs. [88][89][90][91][92][93][94][95][96][97][98][99][100][101]. Shortly, the essence of Regge-Wheeler method consists in the following (one can find details in refs.…”

Section: Jcap01(2023)005mentioning

confidence: 99%

Anti-de Sitter neutron stars in the theory of gravity with nonminimal derivative coupling

Kashargin

Sushkov

2023

We consider neutron star configurations in the scalar-tensor theory of gravity with the coupling between the kinetic term of a scalar field and the Einstein tensor (such the model is a subclass of Horndeski gravity). Neutron stars in this model were studied earlier for the special case with a vanishing “bare” cosmological constant, Λ0 = 0, and a vanishing standard kinetic term, α = 0. This special case is of interest because it admits so-called stealth configuration, i.e. vacuum configuration with nontrivial scalar field and the Schwarzschild metric. However, generally one has Λ0 ≠ 0 and α ≠ 0 and in this case a vacuum configuration is represented as an asymptotically anti-de Sitter (AdS) black hole solution with the nontrivial scalar field. We construct neutron star configurations in this general case and show that resulting diagrams describing the relation between mass and radius of the star essentially differ from those obtained in GR or the particular model with α = Λ0 = 0. Instead, the mass-radius diagrams are similar to those obtained for so-called bare strange stars when a star radius decreases monotonically with decreasing mass. We show also that neutron stars in the theory of gravity with nonminimal derivative coupling are more compact comparing to those in GR or the particular model with α = Λ0 = 0 and suggest a way to estimate possible values of the parameter of nonminimal coupling ℓ. At last, using the Regge-Wheeler method, we discuss briefly the stability of obtained neutron star configurations.

“…In [31,33,34,128,142], evidence has accumulated that scalar-field interactions which break shift symmetry are not generated by asymptotically safe quantum gravity and may thus be set to zero consistently. Shift-symmetric Horndeski models were previously considered in the context of cosmological [28][29][30] and hairy black hole solutions [211][212][213].…”

Section: Truncation: Shift-symmetric Kinetic Braidingsmentioning

confidence: 99%

Shift-symmetric Horndeski gravity in the asymptotic-safety paradigm

Eichhorn

Santos

Wagner

2023

Horndeski gravity is a popular contender for a phenomenological model of dynamical dark energy, and as such subject to observational constraints. In this work, we ask whether Horndeski gravity can be more than a phenomenological model and instead become a fundamental theory, which extends towards high energy scales and includes quantum effects. We find that within the asymptotic-safety paradigm, an ultraviolet completion of a simple class of models of Horndeski gravity is achievable, but places strong constraints on the couplings of the theory. These constraints are not compatible with dynamical dark energy. Further, we find a similar result in an effective-field theory approach to this class of models of Horndeski gravity: under the assumption that there is no new strongly-coupled physics below the Planck scale, quantum gravity fluctuations force the Horndeski couplings to be too small to achieve an explanation of dynamical dark energy.