标题： 关于全局de Sitter空间的粒子创生不稳定性 显示英文标题

标题： On the Instability of Global de Sitter Space to Particle Creation

摘要： 我们证明了即使是对于无自相互作用的 massive 自由场理论，全局de Sitter空间仍然会由于粒子产生而不稳定。 O(4,1) de Sitter 不变量态在渐近过去和未来都是粒子与反粒子解的确定性的相位相干叠加态，因此它不是一个真正的真空态。 在恒定均匀电场导致粒子产生的密切相关的案例中，构造了一个类似于de Sitter不变量态的时间对称态，它同样不是一个稳定的真空态。 我们提供了描述粒子产生过程所需的通用框架，包括平均粒子数以及能量动量张量和电流等动力学量，并且在实时情况下建立了与kinetic理论的联系，适用于de Sitter背景和电场背景。 我们计算了de Sitter空间中绝热真空态的能量动量张量，这些状态在全局S^3截面上于早期时间初始化，并且展示了收缩阶段中的粒子产生会在之后的时间导致极大的能量密度，这需要考虑它们的后向反馈效应，并在膨胀阶段开始之前导致时空大幅偏离全局de Sitter空间。 显示英文摘要

摘要： We show that global de Sitter space is unstable to particle creation, even for a massive free field theory with no self-interactions. The O(4,1) de Sitter invariant state is a definite phase coherent superposition of particle and anti-particle solutions in both the asymptotic past and future, and therefore is not a true vacuum state. In the closely related case of particle creation by a constant, uniform electric field, a time symmetric state analogous to the de Sitter invariant one is constructed, which is also not a stable vacuum state. We provide the general framework necessary to describe the particle creation process, the mean particle number, and dynamical quantities such as the energy-momentum tensor and current of the created particles in both the de Sitter and electric field backgrounds in real time, establishing the connection to kinetic theory. We compute the energy-momentum tensor for adiabatic vacuum states in de Sitter space initialized at early times in global S^3 sections, and show that particle creation in the contracting phase results in exponentially large energy densities at later times, necessitating an inclusion of their backreaction effects, and leading to large deviation of the spacetime from global de Sitter space before the expanding phase can begin.