Over 30?years ago, Barrow and Tipler proposed the principle according to which the action integrated over the entire four-manifold describing the universe should be finite. Here we explore the cosmological consequences of a related criterion, namely, that semiclassical transition amplitudes from the early universe up to current field values should be well defined. On a classical level, our criterion is weaker than the Barrow-Tipler principle, but it has the advantage of being sensitive to quantum effects. We find significant consequences for early universe models, in particular, eternal inflation and strictly cyclic universes are ruled out. Within general relativity, the first phase of evolution cannot be inflationary, and it can be ekpyrotic only if the scalar field potential is trustworthy over an infinite field range. Quadratic gravity eliminates all nonaccelerating backgrounds near a putative big bang (thus imposing favorable initial conditions for inflation), while the expected infinite series of higher-curvature quantum corrections eliminates Lorentzian big bang spacetimes altogether. The scenarios that work best with the principle of finite amplitudes are the no-boundary proposal, which gives finite amplitudes in all dynamical theories that we have studied, and string-inspired loitering phases. We also comment on the relationship of our proposal to the swampland conjectures.
展开▼
机译：超过30年？几年前，Barrow和Tipler提出了根据该原则，根据该原则，在整个四流形描述宇宙中的行动应该是有限的。在这里，我们探讨了相关标准的宇宙学后果，即，应该良好地定义来自早期宇宙的半定类转变幅度，从而达到当前场值。在经典水平上，我们的标准比Barrow-Tipler原理弱，但它具有对量子效应敏感的优点。我们发现对早期宇宙模型的重大后果，特别是，排除了永恒的通货膨胀和严格的循环宇宙。在一般相对性中，速度的第一阶段不能是通货膨胀的，只有在标量域电位在无限场范围上值得信赖。二次重力消除了推定的大爆炸附近的所有非燃道背景（因此对通胀施加有利的初始条件），而预期的无限系列的高曲率量子校正完全消除了Lorentzian Big Bang Spetimes。最佳用有限幅度原则工作的场景是无边界建议，其在我们研究的所有动态理论中提供有限幅度，以及串波动的游荡阶段。我们还对我们对Swampland猜想的建议的关系发表评论。
展开▼
