论文标题
分析半经典制度中的量子重力溢出
Analyzing quantum gravity spillover in the semiclassical regime
论文作者
论文摘要
将量子重力(QG)效应纳入半经典分析的标准方法之一是采用QG模型引起的量子校正时空的概念。该过程假设度量变量的期望值有效地捕获了半经典制度中相关的QG微妙之处。我们研究了这种有效的几何方法的生存能力,以尘埃占主导地位,并以深色能量为主导的宇宙。我们为几何可观测物编写了相位空间表达式,并构造了相应的Hermitian操作员。考虑了这些可观察物的一般操作员排序,并针对单位不断发展的波数据包计算其期望值。在尘埃占主导地位的宇宙的情况下,哈勃参数的期望值与“半经典”表达式匹配,即从规模因子预期值计算出的表达式。在RICCI标量的情况下,半经典表达和量子期望之间的相对差异在奇异之处最大,并且衰减很晚。对于宇宙驱动的宇宙,半经典表达式和期望值之间的差异最为明显,远离弹跳点,暗示了较晚的持续量子效应。与分布形状相关的参数是这些模型中的控制参数。在峰值分布的极限下,可观测值的期望值与它们的半经典对应物匹配,并且使用有效的几何方法的使用是合理的。
One of the standard approaches of incorporating the quantum gravity (QG) effects into the semiclassical analysis is to adopt the notion of a quantum-corrected spacetime arising from the QG model. This procedure assumes that the expectation value of the metric variable effectively captures the relevant QG subtleties in the semiclassical regime. We investigate the viability of this effective geometry approach for the case of dust dominated and a dark energy dominated universe. We write the phase space expressions for the geometric observables and construct corresponding Hermitian operators. A general class of operator ordering of these observables is considered, and their expectation values are calculated for a unitarily evolving wave packet. In the case of dust dominated universe, the expectation value of the Hubble parameter matches the "semiclassical" expression, the expression computed from the scale factor expectation value. In the case of Ricci scalar, the relative difference between the semiclassical expression and quantum expectation is maximum at singularity and decays for late time. For a cosmological constant driven universe, the difference between the semiclassical expressions and the expectation value is most pronounced far away from the bounce point, hinting at the persistent quantum effect at the late time. The parameter related to the shape of the distribution appears as a control parameter in these models. In the limit of a sharply peaked distribution, the expectation value of the observables matches with their semiclassical counterpart, and the usage of effective geometry approach is justified.