We have considered a spatially flat, homogeneous and isotropic FLRW universe filled with a single fluid, known as logotropic dark fluid (LDF), whose pressure evolves through a logarithmic equation-of-state. We use the recent Pantheon SNIa and cosmic chronometer datasets to constrain the parameters of this model, the present fraction of DM [Formula: see text] and the Hubble constant [Formula: see text]. We find that the mean values of these parameters are [Formula: see text] and [Formula: see text] at the [Formula: see text] CL. We also find that the LDF model shows a smooth transition from the deceleration phase to acceleration phase of the universe in the recent past. We note that the redshift of this transition [Formula: see text] ([Formula: see text] error) and is well consistent with the present observations. Interestingly, we find that the universe will settle down to a [Formula: see text]CDM model in future and there will not be any future singularity in the LDF model. Furthermore, we notice that there is no significant difference between the LDF and [Formula: see text]CDM models at the present epoch, but the difference (at the percent level) between these models is found as the redshift increases. We have also studied the generalized second law of thermodynamics at the dynamical apparent horizon for the LDF model with the Bekenstein and Viaggiu entropies.

中文翻译：

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同向暗流体：观察和热力学约束

我们已经考虑了一个空间平坦、均匀且各向同性的 FLRW 宇宙，其中充满了一种称为同向暗流体 (LDF) 的单一流体，其压力通过对数状态方程演变。我们使用最近的万神殿 SNIa 和宇宙天文钟数据集来约束这个模型的参数，DM 的当前分数 [公式：见文本] 和哈勃常数 [公式：见文本]。我们发现这些参数的平均值是 [公式：见文本] 和 [公式：见文本] 在 [公式：见文本] CL。我们还发现，LDF 模型显示了近期宇宙从减速阶段到加速阶段的平稳过渡。我们注意到这种转变的红移[公式：见文本]（[公式：见文本]错误）并且与目前的观察结果非常一致。有趣的是，我们发现未来宇宙会稳定到[公式：见正文]CDM模型，未来LDF模型不会有任何奇点。此外，我们注意到当前时代的 LDF 和 [公式：见文本]CDM 模型之间没有显着差异，但是随着红移的增加，发现这些模型之间的差异（在百分比水平上）。我们还研究了具有 Bekenstein 和 Viaggiu 熵的 LDF 模型在动力学视界的广义热力学第二定律。但是随着红移的增加，发现这些模型之间的差异（在百分比水平上）。我们还研究了具有 Bekenstein 和 Viaggiu 熵的 LDF 模型在动力学视界的广义热力学第二定律。但是随着红移的增加，发现这些模型之间的差异（在百分比水平上）。我们还研究了具有 Bekenstein 和 Viaggiu 熵的 LDF 模型在动力学视界的广义热力学第二定律。