# "Power-laws f(R) theories are cosmologically unacceptable"

Abstract : In the recent paper astro-ph/0603703 we have shown that $f(R)=R+\mu R^n$ modified gravity dark energy models are not cosmologically viable because during the matter era that precedes the accelerated stage the cosmic expansion is $a ~ t^{1/2}$ rather than $t^{2/3}$. In this short note we wish to comment on the recent paper astro-ph/0604431 which criticised our results. We show here that the $R^n$ models presented in astro-ph/0604431 cannot generate a stage with $a ~ t^{2/3}$ preceding a stage of accelerated expansion. Hence, though acceptable $f(R)$ dark energy models might exist, the $R^n$ models presented in astro-ph/0604431 are not viable, confirming our previous results.
Document type :
Journal articles
Domain :

http://hal.in2p3.fr/in2p3-00115597
Contributor : Dominique Girod <>
Submitted on : Wednesday, November 22, 2006 - 10:48:51 AM
Last modification on : Tuesday, November 19, 2019 - 9:08:02 PM

### Citation

L. Amendola, D. Polarski, S. Tsujikawa. "Power-laws f(R) theories are cosmologically unacceptable". International Journal of Modern Physics D, World Scientific Publishing, 2007, 16, pp.1555-1561. ⟨10.1142/S0218271807010936⟩. ⟨in2p3-00115597⟩

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