Unifying inflation with ΛCDM epoch in modified f(R) gravity consistent with Solar System tests

Abstract

We suggest two realistic f (R) and one F (G) modified gravities which are consistent with local tests and cosmological bounds. The typical property of such theories is the presence of the effective cosmological constant epochs in such a way that early-time inflation and late-time cosmic acceleration are naturally unified within single model. It is shown that classical instability does not appear here and Newton law is respected. Some discussion of possible anti-gravity regime appearence and related modification of the theory is done. 95.36.+x,

Observational constraints on kinetic gravity braiding from the integrated Sachs-Wolfe effect

“…This is because the ISW effect anti-correlates with the LSS for n < O(1000), and the sign of the cross-correlation function determines the lower bound (15). Note that the galaxy bias in Ref.…”

“…Therefore, this is not problematic, and we also confirmed that using the galaxy bias of the ΛCDM model does not significantly change the results of chi-squared analysis. The lower bound (15) changes within only 10 percent even when we assume the bias as free parameters. This is because the constraint on the model parameter n is determined by the sign of the cross-correlation function, which is almost independent of nature of bias.…”

“…A number of modified gravity models have been proposed so far, including scalar-tensor theories, f (R) gravity [9][10][11][12][13][14][15], the Dvali-Gabadadze-Porrati (DGP) brane model [16,17], and galileon gravity [18].…”

Linearized treatment of scalar perturbations in the Asymptotic Cosmological Model

“…In particular, if the conformal equivalence between f (R) theories and scalar-tensor theories is used, it is necessary that the effective mass acquired by the new scalar degree of freedom is unnaturally large [30]. Some f (R) theories that pass cosmological and solar system tests have been proposed [31][32][33]. However, it is also subject of debate if the conformal equivalence can be used in order to extract physical predictions from this models, especially predictions which involve perturbations [34].…”

Revised Spherically Symmetric Solutions of R+ε/R Gravity

“…Since the Schwarzschild metric is consistent with observations of the solar system, spherically symmetric solutions of a viable theory of f(R) gravity for the vacuum should have a satisfactory limit of Schwarzschild metric. As yet, the discussion on the weak field limit of this f (R) = R + µ 4 /R theory of gravity is done and there are a few papers which claim different results [13][14][15][16][17][18][19][20]. In the recent works, authors have discussed f (R) = R ± µ 4 /R theory of gravity for the case of weak field limit and obtained perturbation terms in the metric potential components which are independent from the localized mass as source of inhomogeneous curvature and initial value conditions [21,22].…”