Quantum gravitational onset of Starobinsky inflation in a closed universe
Quantum gravitational onset of Starobinsky inflation in a closed universe
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DOI：
10.1103/physrevd.103.046016
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发表时间：
2020-10
影响因子：
5
通讯作者：
Lucia Gordon;Bao-Fei Li;Parampreet Singh
中科院分区：
文献类型：
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作者：
Lucia Gordon;Bao-Fei Li;Parampreet Singh
最近的宇宙微波背景观测支持封闭宇宙中的低能尺度暴胀模型。然而，在封闭宇宙的这种模型中，暴胀的开始是有严重问题的。特别是，当初始条件在普朗克范围内给定时，这样的宇宙在几个普朗克秒内就会发生坍缩，并遇到一个大坍缩奇点。我们表明，在低能量尺度的通货膨胀模型的通货膨胀的发病问题，可以成功地克服在量子引力的框架下，大爆炸/大紧缩奇异性解决和非奇异的循环演化之前存在的通货膨胀。作为一个例子，我们考虑了一个模型在循环量子宇宙学和证明，成功的低能量尺度的膨胀在一个封闭的宇宙中的Starobinsky暴胀模型从各种初始条件，这是不可能的，在经典理论的开始是可能的。为了比较，我们也研究了在非常不利的条件下暴胀模型中暴胀的开始，并发现了类似的结果。包括相空间分析在内的数值研究表明，具有量子引力效应的预暴胀相由非全同的反弹周期和非全同的周期组成，从而导致类暴胀现象，这在创造适当的条件使暴胀在一定数量的非奇异周期后发生方面起着重要作用.我们的分析表明，经典理论中的张力相当于封闭的Friedmann-Lema\^{\i}tre-Robertson-步行者宇宙相对于低能尺度暴胀的开始的不适合性，可以在圈量子宇宙学中成功地解决。
Recent cosmic microwave background observations favor low-energy-scale inflationary models in a closed universe. However, the onset of inflation in such models for a closed universe is known to be severely problematic. In particular, such a universe recollapses within a few Planck seconds and encounters a big crunch singularity when initial conditions are given in the Planck regime. We show that this problem of the onset of inflation in low-energy-scale inflationary models can be successfully overcome in a quantum-gravitational framework where the big bang/big crunch singularities are resolved and a nonsingular cyclic evolution exists prior to inflation. As an example, we consider a model in loop quantum cosmology and demonstrate that the successful onset of low-energy-scale inflation in a closed universe is possible for the Starobinsky inflationary model starting from a variety of initial conditions where it is impossible in the classical theory. For comparison, we also investigate the onset of inflation in the ${\ensuremath{\phi}}^{2}$ inflationary model under highly unfavorable conditions and find similar results. Our numerical investigation including the phase-space analysis shows that the preinflationary phase with quantum gravity effects is composed of nonidentical cycles of bounces and recollapses resulting in a hysteresis-like phenomenon, which plays an important role in creating suitable conditions for inflation to occur after some number of nonsingular cycles. Our analysis shows that the tension in the classical theory amounting to the unsuitability of closed Friedmann-Lema\^{\i}tre-Robertson-Walker universes with respect to the onset of low-energy-scale inflation can be successfully resolved in loop quantum cosmology.