Black holes in self-tuning cubic Horndeski cosmology

Emond, William T.; Lehébel, Antoine; Saffin, Paul M.

doi:10.1103/physrevd.101.084008

Cited by 13 publications

(12 citation statements)

References 39 publications

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“…While the cubic Galileon model with G ∝ X φ has been ruled out through constraints from ISW, BAO and CMB data [25], [26], [27], the particular form of G in our model has not yet been compared with observations. A related model, mainly lacking the linear potential, was recently studied in the context of black holes in cubic Horndeski theories [28].…”

Section: The Minimal Self-tuning Modelmentioning

confidence: 99%

A minimal self tuning model to solve the cosmological constant problem

Khan¹,

Taylor²

2022

Preprint

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The expansion of the Universe is observed to be accelerating, with the simplest solution being a classical cosmological constant. However, this receives contributions from the quantum vacuum, which are predicted to be many orders of magnitude larger than observations, and suffers from radiative instabilities requiring repeated fine-tuning. In this paper we present a minimal, self-tuning scalar field model that can dynamically cancel a large quantum vacuum energy, avoiding Weinberg's No-Go Theorem, and produce accelerated de Sitter expansion at a lower energy scale as a solution to the problem. Our minimal model, which contains a non-canonical kinetic energy and a linear potential, belongs to the Kinetic Gravity Braiding sub-class of Horndeski theory which is not observationally excluded, and lies outside of the known Fab-Four or Well-Tempered models. We find analytic solutions in the limits of slow-roll and fast-roll, and numerically solve the equations of motion to illustrate our model. We show that the model allows for a matter dominated era, and that the attractor solution is stable under a phase transition in the vacuum energy density. We also consider the energyscales required to match observations. Our model shows the existence of a wider class of successful self-tuning models than previously assumed.

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Section: The Minimal Self-tuning Modelmentioning

confidence: 99%

A minimal self tuning model to solve the cosmological constant problem

Khan¹,

Taylor²

2022

Preprint

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“…where g 2 and g 3 are arbitrary coupling constants with dimensions of Length 2 that we can tune. These or similar choices have been considered in the literature before, namely in models of dark energy [50,[53][54][55][56][57], and in studies of the fate of the Universe in cosmological bounces or inflationary models [56,[58][59][60], among others [61,62].…”

Section: Cases Exploredmentioning

confidence: 99%

Gravitational Collapse in Cubic Horndeski Theories

Figueras,

França

2020

Preprint

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We study spherically symmetric gravitational collapse in cubic Horndeski theories of gravity. By varying the coupling constants and the initial amplitude of the scalar field, we determine the region in the space of couplings and amplitudes for which it is possible to construct global solutions to the Horndeski theories. Furthermore, we identify the regime of validity of effective field theory as the sub-region for which a certain weak field condition remains small at all times. We evolve the initial data using the CCZ4 formulation of the Einstein equations and horizon penetrating coordinates without assuming spherical symmetry.

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“…Recent results even show that the Galileon ghost condensate [25] and the generalized cubic covariant Galileon [26] theories of the tadpole-free shift symmetric sector of KGB can be as compatible with cosmological observations as the ΛCDM model. Interestingly, the same sector also houses hairy black holes and could be potentially rich with observational signatures from the strong gravity regime [27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Self-tuning kinetic gravity braiding: Cosmological dynamics, shift symmetry, and the tadpole

Bernardo

2021

Preprint

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We study the self-tuning subclass of kinetic gravity braiding and obtain robust predictions on self-tuning and dynamics in the tadpole-free shift symmetric sector of the theory. In particular, we show inevitability of cosmic acceleration, prove the dynamical stability of this late-time asymptotic state, and derive ghost and gradient stability constraints on the self-tuning vacuum. We discuss the results concretely in the context of generalized cubic covariant Galileon theory and an exponential kinetic gravity braiding.

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Black holes in self-tuning cubic Horndeski cosmology

Cited by 13 publications

References 39 publications

A minimal self tuning model to solve the cosmological constant problem

A minimal self tuning model to solve the cosmological constant problem

Gravitational Collapse in Cubic Horndeski Theories

Self-tuning kinetic gravity braiding: Cosmological dynamics, shift symmetry, and the tadpole

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