# CMB acoustic scale in the entropic-like accelerating universe - General Relativity and Quantum Cosmology

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Abstract: We consider generalizations of the entropic accelerating universe recentlyproposed in Ref. 4,5 and show that their background equations can be madeequivalent to a model with a dark energy component with constant parameter ofstate $w {X} = -1 + 2\, \gamma -3$, where $\gamma$ is related to thecoefficients of the new terms in the Friedman equations. After discussing allthe Friedman equations for an arbitrary $\gamma$, we show how to recover thestandard scalings for dust and radiation. The acoustic scale $\ell A$, relatedto the peak positions in the pattern of the angular power spectrum of theCosmic Microwave Background anisotropies, is also computed and yields thestringent bound $|\gamma|\ll 1$. We then argue that future data might be ableto distinguish this model from pure $\Lambda$CDM corresponding to $\gamma=0$.