Novel higher-curvature variations of 
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 inflation

Cano, Pablo A.; Fransen, Kwinten; Hertog, Thomas

doi:10.1103/physrevd.103.103531

Cited by 20 publications

(17 citation statements)

References 79 publications

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“…It is in this sense that the energy conditions are discussed in this section. Moreover, since 13 In the context of effective field theory approaches to modifying GR, higher-curvature corrections that yield at most second-order EOMs on an FLRW background have been explored in [74]. An interesting observation is made: the resulting theory is modified in a very similar fashion to what is found in the string theory context of this paper with an infinite tower of α corrections.…”

Section: Effective Energy Conditions and Their Violationmentioning

confidence: 61%

Cosmology at the top of the α′ tower

Quintin

Bernardo

Franzmann

2021

J. High Energ. Phys.

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The cosmology of the fully α′-corrected duality-invariant action for the Neveu-Schwarz sector of string theory is revisited, with special emphasis on its coupling to matter sources. The role of the duality covariant pressure and dilatonic charge of the matter sector is explored in various contexts, from the low-curvature regime to non-perturbative solutions in α′. We comment on how an infinite tower of α′ corrections allows for fixed-dilaton de Sitter solutions, even in vacuum. We further investigate the necessary conditions for accelerated expansion in the Einstein frame, as well as for non-singular bounces that could resolve the big bang singularity. In particular, explicit examples are constructed, which show that the tower of α′ corrections may support an Einstein-frame non-singular cosmological bouncing background, even when the matter sector respects the null energy condition.

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Section: Effective Energy Conditions and Their Violationmentioning

confidence: 61%

Cosmology at the top of the α′ tower

Quintin

Bernardo

Franzmann

2021

J. High Energ. Phys.

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“…To this regard, the current model have to be considered only as an effective theory and needs to be analyzed from this point of view. An expanded discussion on this issue is presented in a recent publication [57].…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, different studies have considered a holographic approach for the Einsteinian cubic gravity [55,56]. Recently, the Starobinsky's model of inflation has been corrected by adding a cubic component [57]. The authors have investigated the slow-roll regime and discussed the possibility of validation, taking into consideration the scalar and tensor perturbations.…”

Section: Introductionmentioning

confidence: 99%

Dark effects in $$\tilde{f}(R,P)$$ gravity

Marciu

2021

Eur. Phys. J. C

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In the present paper a new cosmological model is proposed by extending the Einstein–Hilbert Lagrangian with a generic functional $$\tilde{f}(R,P)$$ f ~ ( R , P ) , which depends on the scalar curvature R and a term P which encodes a possible influence from specific cubic contractions of the Riemann tensor. After proposing the corresponding action, the associated modified Friedmann relations are deduced, in the case where the generic functional has the following decomposition, $$\tilde{f}(R,P)=f(R)+g(P)$$ f ~ ( R , P ) = f ( R ) + g ( P ) . The present study takes into account the power-law and the exponential decomposition for the specific form of the corresponding generic functional. For the analytical approach the specific method of dynamical system analysis is employed, revealing the fundamental properties of the phase space structure, discussing the dynamical consequences for the cosmological solutions obtained. It is revealed that the cosmological solutions associated to the critical points can explain various dynamical eras, with a high sensitivity to the values of the corresponding parameters, encoding different effects due to the geometrical nature of the specific couplings.

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“…3. Although the defining property pertains to static spherically symmetric black holes, certain subsets of GQTGs allow for reduction of order in the field equations for other metrics, such as Taub-NUT/Bolt [39], slowly-rotating black holes [59,83], near extremal black holes [50], and cosmological solutions [43][44][45]72].…”

Section: Introductionmentioning

confidence: 99%

Generalized quasi-topological gravities: the whole shebang

Bueno¹,

Cano²,

Hennigar³

et al. 2022

Preprint

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Generalized quasi-topological gravities (GQTGs) are higher-curvature extensions of Einstein gravity in D-dimensions. Their defining properties include possessing second-order linearized equations of motion around maximally symmetric backgrounds as well as non-hairy generalizations of Schwarzschild's black hole characterized by a single function, f (r) ≡ −g tt = g −1 rr , which satisfies a second-order differential equation. In arXiv:1909.07983 GQTGs were shown to exist at all orders in curvature and for general D. In this paper we prove that, in fact, n − 1 inequivalent classes of order-n GQTGs exist for D ≥ 5. Amongst these, we show that one -and only one-type of densities is of the Quasi-topological kind, namely, such that the equation for f (r) is algebraic. Our arguments do not work for D = 4, in which case there seems to be a single unique GQT density at each order which is not of the Quasi-topological kind. We compute the thermodynamic charges of the most general D-dimensional order-n GQTG, verify that they satisfy the first law and provide evidence that they can be entirely written in terms of the embedding function which determines the maximally symmetric vacua of the theory.

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Novel higher-curvature variations of R2 inflation

Cited by 20 publications

References 79 publications

Cosmology at the top of the α′ tower

Cosmology at the top of the α′ tower

Dark effects in $$\tilde{f}(R,P)$$ gravity

Generalized quasi-topological gravities: the whole shebang

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