论文标题
部分可观测时空混沌系统的无模型预测
Universal accelerating cosmologies from 10d supergravity
论文作者
论文摘要
我们研究4D Friedmann-Lema-Robertson-Walker-Walker宇宙学从各种6D歧管的IIA型10D超级重压获得（Calabi-Yau，Einstein，Einstein-Kähler）。我们提出的宇宙学是普遍的，因为它们不取决于紧凑型歧管的详细特征，而仅取决于属于该类别的所有歧管所共有的属性。一旦将运动方程式重写为适当的动力系统，就可以体现出具有加速扩展阶段的解决方案的存在。该动力系统的固定点以及相空间边界上的轨迹对应于我们明确确定的分析解决方案。此外，某些结果的宇宙学表现出永恒或半端的加速度，而其他宇宙学则可以对电子折叠数量进行参数控制。在将来的无穷大，可以同时实现大容量和弱弦耦合。此外，我们发现了几种没有大爆炸奇点的平稳加速宇宙学：宇宙在宇宙学的过去（$ t <0 $）都在收缩，将来会扩展（$ t> 0 $），而在$ t = 0 $的附近，它成为了毛质切片的Sitter。我们还获得了几种宇宙学，其中包括无限数量的加速和减速膨胀周期的循环。
We study 4d Friedmann-Lemaître-Robertson-Walker cosmologies obtained from time-dependent compactifications of Type IIA 10d supergravity on various classes of 6d manifolds (Calabi-Yau, Einstein, Einstein-Kähler). The cosmologies we present are universal in that they do not depend on the detailed features of the compactification manifold, but only on the properties which are common to all the manifolds belonging to that class. Once the equations of motion are rewritten as an appropriate dynamical system, the existence of solutions featuring a phase of accelerated expansion is made manifest. The fixed points of this dynamical system, as well as the trajectories on the boundary of the phase space, correspond to analytic solutions which we determine explicitly. Furthermore, some of the resulting cosmologies exhibit eternal or semi-eternal acceleration, whereas others allow for a parametric control on the number of e-foldings. At future infinity, one can achieve both large volume and weak string coupling. Moreover, we find several smooth accelerating cosmologies without Big Bang singularities: the universe is contracting in the cosmological past ($T<0$), expanding in the future ($T>0$), while in the vicinity of $T=0$ it becomes de Sitter in hyperbolic slicing. We also obtain several cosmologies featuring an infinite number of cycles of alternating periods of accelerated and decelerated expansions.
