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arXiv · 1708.08631

A new test of $f(R)$ gravity with the cosmological standard rulers in radio quasars

Tengpeng Xu·Shuo Cao·Jingzhao Qi·Marek Biesiada·Xiaogang Zheng·Zong-Hong Zhu
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Abstract

As an important candidate gravity theory alternative to dark energy, a class of $f(R)$ modified gravity, which introduces a perturbation of the Ricci scalar $R$ in the Einstein-Hilbert action, has been extensively applied to cosmology to explain the acceleration of the universe. In this paper, we focus on the recently-released VLBI observations of the compact structure in intermediate-luminosity quasars combined with the angular-diameter-distance measurements from galaxy clusters, which consists of 145 data points performing as individual cosmological standard rulers in the redshift range $0.023\le z\le 2.80$, to investigate observational constraints on two viable models in $f(R)$ theories within the Palatini formalism: $f_1(R)=R-\frac{a}{R^b}$ and $f_2(R)=R-\frac{aR}{R+ab}$. We also combine the individual standard ruler data with the observations of CMB and BAO, which provides stringent constraints. Furthermore, two model diagnostics, $Om(z)$ and statefinder, are also applied to distinguish the two $f(R)$ models and $Λ$CDM model. Our results show that (1) The quasars sample performs very well to place constraints on the two $f(R)$ cosmologies, which indicates its potential to act as a powerful complementary probe to other cosmological standard rulers. (2) The $Λ$CDM model, which corresponds to $b=0$ in the two $f(R)$ cosmologies is still included within $1σ$ range. However, there still exists some possibility that $Λ$CDM may not the best cosmological model preferred by the current high-redshift observations. (3) The information criteria indicate that the cosmological constant model is still the best one, while the $f_1(R)$ model gets the smallest observational support. (4) The $f_2(R)$ model, which evolves quite different from $f_1(R)$ model at early times, still significantly deviates from both $f_1(R)$ and $Λ$CDM model at the present time.

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Tengpeng Xu, Shuo Cao, Jingzhao Qi, Marek Biesiada, Xiaogang Zheng, Zong-Hong Zhu. 2018-06-19. A new test of $f(R)$ gravity with the cosmological standard rulers in radio quasars. https://doi.org/10.1088/1475-7516%2F2018%2F06%2F042

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