Cuscuton gravity as a classically stable limiting curvature theory

Quintin, Jerome; Yoshida, Daisuke

doi:10.1088/1475-7516/2020/02/016

Cited by 39 publications

(36 citation statements)

References 167 publications

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“…On the other hand, the cuscuton dynamics, which has been studied in Refs. [52][53][54] to find exact solution describing an accelerating fourdimensional universe with a stable extra dimension [52], the possibility to construct analytic solutions for the cosmological background evolution that mimics CDM cosmology [53], and the cuscuton gravity as a classically stable limiting curvature theory [54], the cuscuton dynamics has also been very recently investigated within the braneworld context in Refs. [55,56].…”

Section: Introductionmentioning

confidence: 99%

Impact of compactlike and asymmetric configurations of thick branes on the scalar–tensor representation of $$f\left( R,T\right) $$ gravity

2022

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In this work we study braneworld models in generalized $$f\left( R,T\right) $$ f R , T gravity theories where the action depends on a function of the Ricci scalar R and the trace of the stress–energy tensor T. We explore the so-called scalar–tensor representation of the theory, where the dependence on R and T are exchanged for two auxiliary real scalar fields. We introduce a first-order formalism to relate the auxiliary fields with the source field of brane and analyze four distinct possibilities of current interest regarding compactification and asymmetry of the brane. We investigate the behavior of the auxiliary fields and their stability in each one of the four cases. For the models where the solution of the source field engenders compact behavior, the auxiliary fields exhibit a hybrid structure, behaving differently inside and outside the compact region described by the source configuration. In particular, we found that the solutions of the auxiliary fields are significantly modified in models where the geometry is strongly influenced by the source field. Moreover, for the model capable of engendering asymmetric features, the two auxiliary fields also respond to modifications on the parameter that controls the asymmetry of the system.

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Section: Introductionmentioning

confidence: 99%

Impact of compactlike and asymmetric configurations of thick branes on the scalar–tensor representation of $$f\left( R,T\right) $$ gravity

2022

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“…Indeed, this instability originates from a scalar degree of freedom, which is expected to be absent in the cuscuton-type theory on a cosmological background (e.g., [56,[59][60][61]). As an example, a nonsingular homogeneous and isotropic bouncing background in mimetic gravity was shown to have instabilities [63], while nonsingular bouncing backgrounds in cuscuton gravity have shown no instability [51,52], at the level of linear inhomogeneous perturbations.…”

Section: Limiting Anisotropy Modelsmentioning

confidence: 99%

“…The original limiting curvature theory [31,32] is not the only way to realize the limiting curvature hypothesis. It was pointed out that mimetic gravity [43][44][45] and cuscuton gravity [46,47] have a structure that limits the Hubble parameter, and hence they possess nonsingular cosmological and black hole solutions [48][49][50][51][52]. One of the critical differences between mimetic and cuscuton theories (and extensions thereof) is the number of degrees of freedom; mimetic gravity has 3 degrees of freedom (e.g., [53][54][55]), while cuscuton gravity has only 2 degrees of freedom on a cosmological background (e.g., [56][57][58][59][60][61]).…”

Section: Introductionmentioning

confidence: 99%

“…2 However, it is expected that this solution is unstable since we know that cosmological solutions are unstable in a large class of mimetic gravity [28,55,[63][64][65][66]. On the other hand, cosmological solutions in cuscuton gravity and its extensions can be stable [47,59,67,68], implying that one can construct stable nonsingular solutions in cuscuton theories [51,52].…”

Section: Introductionmentioning

confidence: 99%

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Theories with limited extrinsic curvature and a nonsingular anisotropic universe

et al. 2020

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We propose a class of theories that can limit scalars constructed from the extrinsic curvature. Applied to cosmology, this framework allows us to control not only the Hubble parameter but also anisotropies without the problem of Ostrogradsky ghost, which is in sharp contrast to the case of limiting spacetime curvature scalars. Our theory can be viewed as a generalization of mimetic and cuscuton theories (thus clarifying their relation), which are known to possess a structure that limits only the Hubble parameter on homogeneous and isotropic backgrounds. As an application of our framework, we construct a model where both anisotropies and the Hubble parameter are kept finite at any stage in the evolution of the universe in the diagonal Bianchi type I setup. The universe starts from a constant-anisotropy phase and recovers Einstein gravity at low energies. We also show that the cosmological solution is stable against a wide class of perturbation wave numbers, though instabilities may remain for arbitrary initial conditions.

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“…A realization of the limiting curvature hypothesis in the context of scalartensor theories is also studied in Refs. [26][27][28]. Unfortunately, the regular black hole in Ref.…”

Section: Introductionmentioning

confidence: 99%

Stability of magnetic black holes in general nonlinear electrodynamics

2020

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We study the perturbative stability of magnetic black holes in a general class of nonlinear electrodynamics, where the Lagrangian is given by a general function of the field strength of electromagnetic field F μν and its Hodge dualF μν . We derive sufficient conditions for the stability of the black holes. We apply the stability conditions to Bardeen's regular black holes, black holes in Euler-Heisenberg theory, and black holes in Born-Infeld theory. As a result, we obtain a sufficient condition for the stability of Bardeen's black holes, which restricts F μνF μν dependence of the Lagrangian. We also show that black holes in Euler-Heisenberg theory are stable for a sufficiently small magnetic charge. Moreover, we prove the stability of black holes in the Born-Infeld electrodynamics even when including F μνF μν dependence.

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Cuscuton gravity as a classically stable limiting curvature theory

Cited by 39 publications

References 167 publications

Impact of compactlike and asymmetric configurations of thick branes on the scalar–tensor representation of $$f\left( R,T\right) $$ gravity

Impact of compactlike and asymmetric configurations of thick branes on the scalar–tensor representation of $$f\left( R,T\right) $$ gravity

Theories with limited extrinsic curvature and a nonsingular anisotropic universe

Stability of magnetic black holes in general nonlinear electrodynamics

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