Clifton's spherical solution in f(R) vacuo harbours a naked singularity

Faraoni, Valerio

doi:10.48550/arxiv.0909.0514

Cited by 2 publications

(5 citation statements)

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“…For other astrophysical solutions and various metric solutions from F (R) gravity and modified gravity in general, see for example Refs. [285,330,452,617,[639][640][641][642][643][644][645][646][647][648].…”

Section: A Neutron and Quark Stars From F (R) Gravitymentioning

confidence: 99%

Modified Gravity Theories on a Nutshell: Inflation, Bounce and Late-time Evolution

Nojiri,

Odintsov,

Oikonomou

2017

Preprint

192

325

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We systematically review some standard issues and also the latest developments of modified gravity in cosmology, emphasizing on inflation, bouncing cosmology and late-time acceleration era. Particularly, we present the formalism of standard modified gravity theory representatives, like F (R), F (G) and F (T ) gravity theories, but also several alternative theoretical proposals which appeared in the literature during the last decade. We emphasize on the formalism developed for these theories and we explain how these theories can be considered as viable descriptions for our Universe. Using these theories, we present how a viable inflationary era can be produced in the context of these theories, with the viability being justified if compatibility with the latest observational data is achieved. Also we demonstrate how bouncing cosmologies can actually be described by these theories. Moreover, we systematically discuss several qualitative features of the dark energy era by using the modified gravity formalism, and also we critically discuss how a unified description of inflation with dark energy era can be described by solely using the modified gravity framework. Finally, we also discuss some astrophysical solutions in the context of modified gravity, and several qualitative features of these solutions. The aim of this review is to gather the different modified gravity techniques and form a virtual modified gravity "toolbox", which will contain all the necessary information on inflation, dark energy and bouncing cosmologies in the context of the various forms of modified gravity.

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Section: A Neutron and Quark Stars From F (R) Gravitymentioning

confidence: 99%

Modified Gravity Theories on a Nutshell: Inflation, Bounce and Late-time Evolution

Nojiri,

Odintsov,

Oikonomou

2017

Preprint

192

325

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“…Having discarded the possibility of having a static exterior spacetime, we shall now analyse one of the simplest non-static ansätze one can possibly conceive: that given by expression (25). However, it is almost immediate to show that the exterior metric cannot be of the form (25). In fact, to prove it, one only needs to realise that junction condition (14) implies that β = β 0 = const.…”

Section: B Proof Of Results 3 4 Andmentioning

confidence: 99%

“…It is almost immediate to check that the third junction condition still leads to equation (17). 24 Finally, the fourth junction condition now yields 25 ξ *…”

Section: Third and Fourth Junction Conditionsmentioning

confidence: 92%

“…Coincidentally, the only solution which remains compatible with all of our results is -as far as we are aware-the Clifton II spacetime [21], which is a solution of these 'power of GR' theories. The Clifton II solution is highly non-trivial [25], and the analysis of the junction conditions following the lines of Appendices B and C seems to be impossible to perform analytically. For these reasons, further (numerical) studies are required in order to determine whether the Clifton II spacetime can be the exterior spacetime corresponding to a collapsing dust star.…”

Section: Conclusion and Future Prospectsmentioning

confidence: 99%

“…(C3) entails that ṙ * = rη * η * + r ξ * ξ * , so the third junction condition is much more convoluted in these coordinates. 25 We would like to remark that, in these coordinates, the Ricci scalar of the exterior solution is given by…”

Section: Third and Fourth Junction Conditionsmentioning

confidence: 99%

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Is gravitational collapse possible in $f(R)$ gravity?

Casado-Turrión,

de la Cruz-Dombriz,

Dobado

2022

Preprint

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Gravitational collapse is still poorly understood in the context of f (R) theories of gravity, since the Oppenheimer-Snyder model is incompatible with their junction conditions. In this work, we will present a systematic approach to the problem. Starting with a thorough analysis of how the Oppenheimer-Snyder construction should be generalised to fit within metric f (R) gravity, we shall subsequently proceed to explore the existence of novel exterior solutions compatible with physically viable interiors. Our formalism has allowed us to show that some paradigmatic vacuum metrics cannot represent spacetime outside a collapsing dust star in metric f (R) gravity. Moreover, using the junction conditions, we have found a novel vacuole solution of a large class of f (R) models, whose exterior spacetime is documented here for the first time in the literature as well. Finally, we also report the previously unnoticed fact that the Oppenheimer-Snyder model of gravitational collapse is incompatible with the Palatini formulation of f (R) gravity.

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Clifton's spherical solution in f(R) vacuo harbours a naked singularity

Cited by 2 publications

References 0 publications

Modified Gravity Theories on a Nutshell: Inflation, Bounce and Late-time Evolution

Modified Gravity Theories on a Nutshell: Inflation, Bounce and Late-time Evolution

Is gravitational collapse possible in $f(R)$ gravity?

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