Download
1 / 12
120 likes | 198 Views
This study delves into f(R) Modified Gravity theories by examining deviations from General Relativity in cosmic acceleration, cosmic structure, and Solar System tests. It explores parameterizations of the expansion history to construct Solar System and Cosmological Local Tests. Observational constraints are considered to distinguish between General Relativity and Modified Gravity, with key quantities and constraints highlighted. The study concludes by discussing the viability of different f(R) models based on their ability to pass various cosmological and Solar System tests.
E N D
f(R) Modified Gravity Cosmological & Solar-System Tests arXiv:1009.3488 Je-An Gu顧哲安 臺灣大學梁次震宇宙學與粒子天文物理學研究中心 Leung Center for Cosmology and Particle Astrophysics (LeCosPA), NTU Collaborators : Wei-Ting Lin林韋廷@ Phys, NTU Dark Energy Working Group @ LeCosPA & NCTS-FGCPA 2010/09/27 COSMO/CosPA @ Tokyo Univ.
f(R) Modified Gravity(MG): Explain cosmic acceleration Model (parameterize) deviation from GR Cosmic Structure Cosmic Expansion Solar-System Test Purposes as an essence of cosmology, need to pass as a theory of modified gravity, need to pass Cosmological Test Local Test
f(R) Modified Gravity(MG): “designer f(R)” FACT For a given expansion history H(t), one can reconstruct f(R) which generates the required H(t). OUR APPROACH with current observational constraints (WMAP7+BAO+SN): Consider the expansion H(t) parametrized via the Chevallier-Polarski-Linderweff(z): Cosmic Structure Cosmic Expansion construct Solar-System Test fini : initial condition of f(R) qj : other cosmological parameters Cosmological Test Local Test
f(R) Modified Gravity(MG): “designer f(R)” FACT For a given expansion history H(t), one can reconstruct f(R) which generates the required H(t). OUR APPROACH Consider the expansion H(t) parametrized via the Chevallier-Polarski-Linderweff(z): Cosmic Structure Cosmic Expansion construct Solar-System Test Cosmological Test Local Test Example weff = 1 f/H02 +6DE fini : initial condition of f(R) qj : other cosmological parameters
f(R) Modified Gravity(MG): Then, proceed to the other two tests of “designer f(R)” OUR APPROACH with observational constraints (WMAP7+BAO+SN): Consider the expansion H(t) parametrized via the Chevallier-Polarski-Linderweff(z): Cosmic Structure Cosmic Expansion construct Solar-System Test Cosmological Test Local Test fini : initial condition of f(R) qj : other cosmological parameters
f(R) Modified Gravity(MG): Key quantities distinguishing GR & MG defined in : Perturbed metric: Evolution eqn. of matter density perturbation: Cosmic Structure Cosmic Expansion late-time, sub-horizon Solar-System Test Cosmological Test Local Test
f(R) Modified Gravity(MG): Cosmological Test Local Test f(R) MG GR late-time, sub-horizon “designer f(R)” Cosmic Structure Cosmic Expansion function of Solar-System Test
f(R) Modified Gravity(MG): Cosmological Test Local Test most f(R) GR Cosmic Structure Cosmic Expansion Solar-System Test E.g. weff = 1 For the present time and k=0.01h/Mpc. / (now) Similar behavior for other weff(z). Observational constraint (Giannantonio et al, 2009):
f(R) Modified Gravity(MG): Cosmological Test Local Test Cosmic Structure Cosmic Expansion Solar-System Test
f(R) Modified Gravity(MG): Constraint on f(R) MG with Chameleon Mechanism survey around GR point parameter space f = constant Viable Cosmic Structure Cosmic Expansion closely mimicking GR+ Solar-System Test Cosmological Test Local Test very small viable region indistinguishable from GR !!
f(R) Modified Gravity(MG): Cosmological Test Local Test GR fRi Cosmic Structure Cosmic Expansion Solar-System Test Constraint on f(R) MG with Chameleon Mechanism The viable f(R) models in the parameter space (weff,fRi) around the GR point (1,0) for constant weff.
Conclusion (observational) Designer w.r.t. the constraint on {w0,wa} (by design) can pass the cosmic-expansion test. The existence of the designer models which pass the cosmic-structure test would require fine-tuning of initial condition fini. Cosmic Structure Cosmic Expansion Solar-System Test Among the designer models, only those closely mimicking GR+ (in all the 3 tests) can pass the solar-system test. As a result, the solar-system test rules out the frequently studied models that are distinct from CDM in .
