### Abstract

Although f(R) modified gravity models can be made to satisfy solar system and cosmological constraints, it has been shown that they have the serious drawback of the nonexistence of stars with strong gravitational fields. In this paper, we discuss whether or not higher curvature corrections can remedy the nonexistence consistently. The following problems are shown to arise as the costs one must pay for the f(R) models that allow for neutrons stars: (i) the leading correction must be fine-tuned to have the typical energy scale μ 10-19GeV, which essentially comes from the free fall time of a relativistic star; (ii) the leading correction must be further fine-tuned so that it is not given by the quadratic curvature term. The second problem is caused because there appears an intermediate curvature scale, and laboratory experiments of gravity will be under the influence of higher curvature corrections. Our analysis thus implies that it is a challenge to construct viable f(R) models without very careful and unnatural fine-tuning.

Original language | English |
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Article number | 024009 |

Journal | Physical Review D - Particles, Fields, Gravitation and Cosmology |

Volume | 79 |

Issue number | 2 |

DOIs | |

Publication status | Published - 2009 Jan 5 |

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### ASJC Scopus subject areas

- Nuclear and High Energy Physics

### Cite this

**Can higher curvature corrections cure the singularity problem in f(R) gravity?** / Kobayashi, Tsutomu; Maeda, Keiichi.

Research output: Contribution to journal › Article

*Physical Review D - Particles, Fields, Gravitation and Cosmology*, vol. 79, no. 2, 024009. https://doi.org/10.1103/PhysRevD.79.024009

}

TY - JOUR

T1 - Can higher curvature corrections cure the singularity problem in f(R) gravity?

AU - Kobayashi, Tsutomu

AU - Maeda, Keiichi

PY - 2009/1/5

Y1 - 2009/1/5

N2 - Although f(R) modified gravity models can be made to satisfy solar system and cosmological constraints, it has been shown that they have the serious drawback of the nonexistence of stars with strong gravitational fields. In this paper, we discuss whether or not higher curvature corrections can remedy the nonexistence consistently. The following problems are shown to arise as the costs one must pay for the f(R) models that allow for neutrons stars: (i) the leading correction must be fine-tuned to have the typical energy scale μ 10-19GeV, which essentially comes from the free fall time of a relativistic star; (ii) the leading correction must be further fine-tuned so that it is not given by the quadratic curvature term. The second problem is caused because there appears an intermediate curvature scale, and laboratory experiments of gravity will be under the influence of higher curvature corrections. Our analysis thus implies that it is a challenge to construct viable f(R) models without very careful and unnatural fine-tuning.

AB - Although f(R) modified gravity models can be made to satisfy solar system and cosmological constraints, it has been shown that they have the serious drawback of the nonexistence of stars with strong gravitational fields. In this paper, we discuss whether or not higher curvature corrections can remedy the nonexistence consistently. The following problems are shown to arise as the costs one must pay for the f(R) models that allow for neutrons stars: (i) the leading correction must be fine-tuned to have the typical energy scale μ 10-19GeV, which essentially comes from the free fall time of a relativistic star; (ii) the leading correction must be further fine-tuned so that it is not given by the quadratic curvature term. The second problem is caused because there appears an intermediate curvature scale, and laboratory experiments of gravity will be under the influence of higher curvature corrections. Our analysis thus implies that it is a challenge to construct viable f(R) models without very careful and unnatural fine-tuning.

UR - http://www.scopus.com/inward/record.url?scp=59249109508&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=59249109508&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.79.024009

DO - 10.1103/PhysRevD.79.024009

M3 - Article

AN - SCOPUS:59249109508

VL - 79

JO - Physical review D: Particles and fields

JF - Physical review D: Particles and fields

SN - 0556-2821

IS - 2

M1 - 024009

ER -