Observational tests of a two parameter power-law class modified gravity in Palatini formalism

Abstract

{\bf{CONTEXT}}: In this work we propose a modified gravity action $f(R)=(R^n-R_0^n{)}^{1/n}$ with two free parameters of $n$ and $R_0$ and derive the dynamics of a universe for this action in the Palatini formalism. {\bf {AIM}}: We do a cosmological comparison of this model with observed data to find the best parameters of a model in a flat universe. {\bf{METHOD}}: To constrain the free parameters of model we use SNIa type Ia data in two sets of gold and union samples, CMB-shift parameter, baryon acoustic oscillation, gas mass fraction in cluster of galaxies, and large-scale structure data. {\bf {RESULT}}: The best fit from the observational data results in the parameters of model in the range of $n=0.98_{-0.08}^{+0.08}$ and ${\Omega }_M=0.25_{+0.1}^{-0.1}$ with one sigma level of confidence where a standard $\Lambda$CDM universe resides in this range of solution. PACS numbers: 04.50.+h, 95.36.+x, 98.80.-k

16 pages, 17 figures

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