A space-time orbifold: A toy model for a cosmological singularity
A space-time orbifold: A toy model for a cosmological singularity
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时空轨道折叠：宇宙奇点的玩具模型
DOI：
10.1103/physrevd.67.026003
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发表时间：
2002
影响因子：
5
通讯作者：
A. Naqvi
中科院分区：
文献类型：
--
作者：
V. Balasubramanian;Sayed Fawad Hassan;E. Keski;A. Naqvi
我们通过时间反转和一些空间反射，在最简单的含时背景下研究玻色弦和II型超弦，即Minkowski空间中的奥比诺德。我们证明了不存在负范数的物理激发。然而，负范数虚态对量子环路的贡献并不抵消，这表明不能选择无鬼规范。频谱包括一个扭曲的扇区，弦被限制在一个在时间上局部化的“圆锥”奇点。由于这些局域化的弦对于渐近观察者是不可见的，因此关于传播态散射的S矩阵的么正性就产生了有趣的问题。我们的模型的配分函数是模不变的，对于超弦，零动量膨胀的蝌蚪是零的。我们研究的许多问题将适用于具有时间局部化奇点的依赖时间的宇宙学背景，我们得出了一些关于在这样的空间上量子化弦的一般性经验。
We explore bosonic strings and Type II superstrings in the simplest time dependent backgrounds, namely orbifolds of Minkowski space by time reversal and some spatial reflections. We show that there are no negative norm physical excitations. However, the contributions of negative norm virtual states to quantum loops do not cancel, showing that a ghost-free gauge cannot be chosen. The spectrum includes a twisted sector, with strings confined to a ``conical'' singularity which is localized in time. Since these localized strings are not visible to asymptotic observers, interesting issues arise regarding unitarity of the S-matrix for scattering of propagating states. The partition function of our model is modular invariant, and for the superstring, the zero momentum dilaton tadpole vanishes. Many of the issues we study will be generic to time-dependent cosmological backgrounds with singularities localized in time, and we derive some general lessons about quantizing strings on such spaces.