We consider the kinematical and dynamical evolution of Friedmann universes with a mixture of non-interacting matter and a ghost-like field, in a scenario analogous to that advocated by the Quintom model. Assuming that the conventional matter dominates today, we find that the ghost component can bring the future expansion and the past contraction of the model to a finite halt. Moreover, at the moment the expansion or contraction stops, we find that the tendency of the universe is to bounce back and re-collapse or re-expand. Therefore, the presence of a (never dominant) ghost-field with negative density could, in principle, drive the universe into an eternal cycle of finite expansion, collapse, and re-expansion. Our study outlines the key features of such a scenario and provides a simple condition for it to occur. We also derive an autonomous set of differential equations and then employ dynamical-system techniques to identify two families of fixed points, with and without spatial curvature respectively. The members of the first family correspond to coasting universes and are stable in the Lyapunov sense. Those of the latter family are unstable repellers when their matter satisfies the strong energy condition and Lyapunov stable in the opposite case.

中文翻译：

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鬼物质宇宙学的运动学和动力学方面

我们考虑了弗里德曼宇宙的运动学和动力学演化，其中包含非相互作用物质和幽灵般的场，类似于 Quintom 模型所倡导的场景。假设今天传统物质占主导地位，我们发现幽灵成分可以使模型的未来扩张和过去收缩陷入有限的停止。而且，在膨胀或收缩停止的那一刻，我们发现宇宙的趋势是反弹并重新坍缩或重新膨胀。因此，原则上，一个（从不占主导地位的）负密度鬼场的存在可以将宇宙推向有限膨胀、坍缩和重新膨胀的永恒循环。我们的研究概述了这种情况的主要特征，并为其发生提供了一个简单的条件。我们还推导出了一组自主微分方程，然后采用动力学系统技术来识别两个固定点系列，分别具有和不具有空间曲率。第一族的成员对应于沿海宇宙，在李雅普诺夫意义上是稳定的。后一族的物质在满足强能量条件时是不稳定的排斥极，反之则为稳定的李雅普诺夫。