论文标题
在以色列 - 斯图尔特形式主义的非线性政权中的粘性宇宙学的定性分析
Qualitative analysis for viscous cosmologies in a non linear regime of the Israel-Stewart formalism
论文作者
论文摘要
我们探讨了宇宙学模型的动力学特性,该模型在平坦的Friedmann-Lemaitre-Robertson-Walker(FLRW)时空中包括流体方程的暗物质扇区中的粘性效应。整个以色列 - 斯图尔特模型的非线性扩展描述了大量的粘性效应。我们允许通过互动术语(即$ Q $)在黑暗领域的能量互换。我们建立了与弗里德曼和与模型相关的方程式相对应的动力系统,并研究其临界点的线性稳定性。从动力学系统中,我们显示了表征非相互作用和相互作用的黑暗扇区中DE Sitter Universe的临界点的外观。我们将研究集中在分析该固定点在大区域的参数空间中的稳定性,并得出周围的线性化解决方案。这些近似和分析的解决方案可能能够描述宇宙的膨胀,因为它们靠近De Sithter Sentary溶液。在具有$ q \ neq 0 $的该策略中,我们意识到该临界点稳定的参数空间中存在区域,并将黑暗能量的行为描述为精髓,宇宙常数和像流体一样的幻影。我们在整个非线性方案中的临界点附近的数值和线性化解决方案之间进行了比较,并将它们与$λ$ CDM模型进行了对比。我们发现,由于参数$ j $的非零值,该观测值完全不受观测,并更接近一致性模型,该值控制了非线性效应。实际上,在低红移值下,与整个非线性状态相关的膨胀速率实际上与$λ$ CDM无法区分。在此制度中获得的减速参数表现出从减速到加速宇宙扩张的过渡。
We explore the dynamical properties of a cosmological model that includes viscous effects in the dark matter sector of the fluid equations in a flat Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime. The bulk viscous effects are described by a non linear extension of the full Israel-Stewart model. We allow the interchange of energy in the dark sector by means of the interaction term, namely $Q$. We establish the dynamical system corresponding to Friedmann and fluid set of equations associated to the model and study the linear stability of its critical points. From the dynamical system, we show the appearance of a critical point characterizing a de Sitter universe within the non interacting and interacting dark sector. We focus our study to analyse the stability of this fixed point in a large region of parameter space and derive linearized solutions around it. These approximate and analytical solutions are potentially able to describe the expansion of the universe since they are close to a de Sitter stationary solution. Within this regime with $Q \neq 0$, we realize the existence of regions in the space of parameters where this critical point is stable and describes the behavior of dark energy as quintessence, cosmological constant and phantom like fluids. We perform a comparison between numerical and linearized solutions nearby the critical points within the full non linear regimes and also contrast them against $Λ$CDM model. We find that fully non linear regime is favored by observations and closer to the concordance model due to the non-zero value of the parameter $j$, which controls the non linear effects. In fact, at low redshift values, the expansion rate associated to the full non linear regime is practically indistinguishable from $Λ$CDM. The deceleration parameter obtained in this regime exhibits a transition from decelerated to accelerated cosmic expansion.