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arXiv · 1604.06908

Dark Energy and Dark Matter from an additional adiabatic fluid

Peter K. S. Dunsby·Orlando Luongo·Lorenzo Reverberi
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Abstract

The Dark Sector is described by an additional barotropic fluid which evolves adiabatically during the universe's history and whose adiabatic exponent $\gamma$ is derived from the standard definitions of specific heats. Although in general $\gamma$ is a function of the redshift, the Hubble parameter and its derivatives, we find that our assumptions lead necessarily to solutions with $\gamma = $ constant in a FLRW universe. The adiabatic fluid acts effectively as the sum of two distinct components, one evolving like non-relativistic matter and the other depending on the value of the adiabatic index. This makes the model particularly interesting as a way of simultaneously explaining the nature of both Dark Energy and Dark Matter, at least at the level of the background cosmology. The $\Lambda$CDM model is included in this family of theories when $\gamma = 0$. We fit our model to SNIa, $H(z)$ and BAO data, discussing the model selection criteria. The implications for the early-universe and the growth of small perturbations in this model are also discussed.

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Peter K. S. Dunsby, Orlando Luongo, Lorenzo Reverberi. 2016-04-23. Dark Energy and Dark Matter from an additional adiabatic fluid. https://doi.org/10.1103/physrevd.94.083525

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