Chern-Simons引力中的真空不稳定性
Vacuum Instability in Chern-Simons Gravity
摘要：
我们探讨了在陈-西蒙斯引力中关于Friedmann-Robertson-Walker背景的扰动。在大动量时，两个圆偏振张量模中的一个模变得像鬼一样。我们认为，尽管如此，该理论并没有表现出经典的失控的解决方案，除了可能在相对论性的非线性制度。然而，鬼模导致真空态是量子力学不稳定的，衰变率是天真的无限大。只有当我们把这个理论解释为一个有效的量子场论时，才能使衰变率是有限的，而这个有效的量子场论直到某个动量截止才成立，这违反了洛伦兹不变性。通过要求在宇宙寿命期间真空衰变产生的光子中的能量密度不违反观测界限，我们得到了对理论的二维参数空间的强约束，包括截止和Chern-Simons质量。
英文摘要：
We explore perturbations about a Friedmann-Robertson-Walker background in Chern-Simons gravity. At large momenta one of the two circularly polarized tensor modes becomes ghostlike. We argue that nevertheless the theory does not exhibit classical runaway solutions, except possibly in the relativistic nonlinear regime. However, the ghost modes cause the vacuum state to be quantum mechanically unstable, with a decay rate that is naively infinite. The decay rate can be made finite only if one interprets the theory as an effective quantum field theory valid up to some momentum cutoff, which violates Lorentz invariance. By demanding that the energy density in photons created by vacuum decay over the lifetime of the Universe not violate observational bounds, we derive strong constraints on the two dimensional parameter space of the theory, consisting of the cutoff and the Chern-Simons mass.
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