Abstract
We suggest that using the first law of thermodynamics is a convenient method to obtain a correct form of the expansion law of the universe (Padmanabhan, arXiv:1206.4916v1 [hep-th]). We will, then, use this idea to obtain the expansion law for a Kodama observer. By using the expansion law for a Kodama observer, we can obtain the dynamic equation of the FRW universe for deformed Horava–Lifshitz gravity. The use of the first law of thermodynamics also leads to a new approach for obtaining the Friedmann equations for f(R) and scalar tensor gravities.
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Dezaki, F.L., Mirza, B. Generalized entropies and the expansion law of the universe. Gen Relativ Gravit 47, 67 (2015). https://doi.org/10.1007/s10714-015-1910-8
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DOI: https://doi.org/10.1007/s10714-015-1910-8