标题： 真正的洛伦兹量子宇宙学 显示英文标题

标题： Truly Lorentzian quantum cosmology

摘要： 基于洛伦兹路径积分的量子宇宙学是一个有前景的方向。 然而，许多先前的研究通过在整个实数线上对平方尺度因子进行积分，允许了非洛伦兹配置。 在这里，我们表明，将迷你超空间路径积分限制为具有正平方尺度因子的洛伦兹配置，可以显著改变期望值。 此外，这使得可以研究因果视界及其量子涨落，并通过排除非洛伦兹的奇异迷你超空间几何来简单地避免奇点。 结果表明，在真正的洛伦兹量子宇宙学中，半经典鞍点近似并不总是有效的。 因此，有关隧穿和无边界提议、反弹宇宙学以及暴胀的量子起源等相关研究需要重新审视。 显示英文摘要

摘要： Quantum cosmology based on Lorentzian path integrals is a promising avenue. However, many previous works allow non-Lorentzian configurations by integrating the squared scale factor over the whole real line. Here we show that restricting the minisuperspace path integral to Lorentzian configurations with positive squared scale factor can significantly change the expectation values. In addition, this enables the study of causal horizons and their quantum fluctuations, and achieves singularity avoidance trivially by excluding singular minisuperspace geometries as non-Lorentzian. The results indicate that semiclassical saddle point approximation is not always valid in truly Lorentzian quantum cosmology. As a consequence, related works on the tunnelling and no-boundary proposals, bouncing cosmology, and the quantum origin of inflation etc. need to be reexamined.