English

Testing generalized logotropic models with cosmic growth

Cosmology and Nongalactic Astrophysics 2021-08-03 v2

Abstract

We check the dynamical and observational features of four typologies of logotropic dark energy models, leading to a \emph{thermodynamic cosmic speed up} fueled by a single fluid that unifies dark energy and dark matter. We first present two principal Anton-Schmidt fluids where the Gr\"uneisen parameter γG\gamma_{\rm G} is free to vary and then fixed to the special value γG=56\gamma_{\rm G}=\tfrac{5}{6}. We also investigate the pure logotropic model, corresponding to γG=16\gamma_{\rm G}=-\frac{1}{6}. Finally, we propose a new logotropic paradigm that works as a generalized logotropic fluid, in which we split the role of dark matter and baryons. We demonstrate that the logotropic paradigms may present drawbacks in perturbations, showing a negative adiabatic sound speed which make perturbations unstable. The Anton-Schmidt model with γG=56\gamma_{\rm G}=\frac{5}{6} is ruled out while the generalized logotropic fluid seems to be the most suitable one, albeit weakly disfavored than the Λ\LambdaCDM model. We combine low- and higher-redshift domains through experimental fits based on Monte Carlo Markov Chain procedures, taking into account supernovae Ia catalogue, Hubble measurements and σ8\sigma_8 data points. We consider two model selection criteria to infer the statistical significance of the four models. We conclude there is statistical advantage to handle the Anton-Schmidt fluid with the Gr\"uneisen parameter free to vary and/or fixed to γG=16\gamma_{\rm G}=-\frac{1}{6}. The generalized logotropic fluid indicates suitable results, statistically favored than the other models, until the sound speed is positive, becoming unstable in perturbations elsewhere. We emphasize that the Λ\LambdaCDM paradigm works statistically better than any kinds of logotropic and generalized logotropic models, while the Chevallier-Polarski-Linder parametrization is statistically comparable with logotropic scenarios.

Cite

@article{arxiv.2103.07252,
  title  = {Testing generalized logotropic models with cosmic growth},
  author = {Kuantay Boshkayev and Talgar Konysbayev and Orlando Luongo and Marco Muccino and Francesco Pace},
  journal= {arXiv preprint arXiv:2103.07252},
  year   = {2021}
}

Comments

15 pages, 3 tables, 4 figures. It matches the published version

R2 v1 2026-06-24T00:03:40.883Z