In order to obtain a better fit for the observational data, various cosmological models have been developed in the literature. For this purpose, we propose an adiabatic expansion of the Universe with a polytropic fluid matter-radiation content and a varying cosmological constant. Basic motivation of this study basically differs from the previous models because our model does not neglect the pressure of the matter content of the Universe. We present the details of our new derivations by obtaining the polytropic matter density and luminosity distances. After constructing the model, two large collections of observational data of supernovae type Ia (SNe Ia) are conducted to diagnose the model. Examining the fitness of our new models of a polytropic universe with the observational data, we find a significant influence of polytropic matter on the cosmological parameters of the expanding universe. We find that our flat constant Λ model and varying Λ model describes the SNe Ia data significantly better than the other models including the standard model for Gold Data and Union2.1 Data, respectively.

中文翻译：

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用 SNe Ia 数据测试多方宇宙模型的绝热膨胀

为了更好地拟合观测数据，文献中已经开发了各种宇宙学模型。为此，我们提出了宇宙的绝热膨胀，具有多方流体物质辐射含量和不同的宇宙学常数。这项研究的基本动机与之前的模型基本不同，因为我们的模型没有忽视宇宙物质含量的压力。我们通过获得多方物质密度和光度距离来展示我们新推导的细节。模型构建完成后，对Ia型超新星(SNe Ia)的两大观测数据进行了模型诊断。用观测数据检查我们的多方宇宙新模型的适应度，我们发现多方物质对膨胀宇宙的宇宙学参数有显着影响。我们发现，我们的平坦常数 Λ 模型和变化的 Λ 模型对 SNe Ia 数据的描述明显优于其他模型，包括 Gold Data 和 Union2.1 Data 的标准模型。