Tsujikawa, Phys. Rev. D 77, 023507 (2008)
Tsujikawa, Phys. Rev. D 77, 023507 (2008) Tsujikawa, Phys. Rev. D 77, 023507 (2008)
Conditions for the viability of f(R) gravity >(1) f 0 (R) > 0f 00 (R) > 0(2) [Dolgov and Kawasaki, Phys. Lett. B 573, 1 (2003)](3)・Positivity of the effective gravitational couplingG eff = G 0 /f 0 (R) > 0 G 0 : Gravitational constant(The graviton is not a ghost.)・ Stability condition: M 2 ù 1/(3f 00 (R)) > 0M : Mass of a new scalar degree of freedom (called the“scalaron”) in the weak-field regime.(The scalaron is not a tachyon.)f(R) → R à 2Λ for R ý R 0R 0Λ: Current curvatureΛ : Cosmological constant・ Realization of the CDM-like behavior in the largecurvature regimeNo. 14Standard cosmology [ Λ + Cold dark matter (CDM)]
(4) Solar system constraintsf(R) gravity[Bertotti, Iess and Tortora,Nature 425, 374 (2003).]・Equivalent[Chiba, Phys. Lett. B 575, 1 (2003)]Brans-Dicke theorywith ω BD =0[Erickcek, Smith and Kamionkowski, Phys. Rev. D 74, 121501 (2006)][Chiba, Smith and Erickcek, Phys. Rev. D 75, 124014 (2007)]However, if the mass of the scalar degree of freedom Mis large, namely, the scalar becomes short-ranged, it hasno effect at Solar System scales.M = M(R)‘‘Chameleon mechanism’’・ Scale-dependence:ω BD : Brans-Dicke parameterObservational constraint: |ω BD | > 40000Cf. [Khoury and Weltman, Phys. Rev. D 69, 044026 (2004)]The scalar degree of freedom may acquire a large effective massat terrestrial and Solar System scales, shielding it fromexperiments performed there.No. 15
- Page 9 and 10: Canonical scalar field >⎧S þ =
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- Page 15 and 16: Data fitting of w(z) >zw(z)=w 0 + w
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- Page 19 and 20: II. Future crossing of the phantom
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- Page 25 and 26: Combined f(T) theory >No. 25u(> 0):
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- Page 41 and 42: We solve Equations (1) and (2) by i
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- Page 66 and 67: Conclusions of Sec. IV >No. 64・
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- Page 70 and 71: No. 45p =0.001p =0.01p = à 0.1p =0
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(4) Solar system constraintsf(R) gravity[Bertotti, Iess and Tortora,Nature 425, 374 (2003).]・Equivalent[Chiba, <strong>Phys</strong>. Lett. B 575, 1 (2003)]Brans-Dicke theorywith ω BD =0[Erickcek, Smith and Kamionkowski, <strong>Phys</strong>. <strong>Rev</strong>. D 74, 121501 (2006)][Chiba, Smith and Erickcek, <strong>Phys</strong>. <strong>Rev</strong>. D 75, 124014 (2007)]However, if the mass of the scalar degree of freedom Mis large, namely, the scalar becomes short-ranged, it hasno effect at Solar System scales.M = M(R)‘‘Chameleon mechanism’’・ Scale-dependence:ω BD : Brans-Dicke parameterObservational constraint: |ω BD | > 40000Cf. [Khoury and Weltman, <strong>Phys</strong>. <strong>Rev</strong>. D 69, 044026 (2004)]The scalar degree of freedom may acquire a large effective massat terrestrial and Solar System scales, shielding it fromexperiments performed there.No. 15
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