论文标题
公制的重力理论中的不稳定性
Instabilities in Metric-Affine Theories of Gravity
论文作者
论文摘要
我们讨论了用高阶曲率术语构建的公制理论的幽灵不稳定性的存在。我们主要关注仅包含RICCI张量的理论，并表明投影对称性的关键作用。病理模式是由于连接中包含的2形场的射击模式的纯动力学项以及非对称重力理论中指标的反对称部分的非最小程度耦合而产生的。重要的耦合被认为是详细的，不能用来使理论稳定。我们讨论不同的程序，以避免鬼魂通过添加其他约束。我们最终争辩说，除非在建设中受到很多注意，否则期望这些病理如何存在于普通公制的理论中。
We discuss the presence of ghostly instabilities for metric-affine theories constructed with higher order curvature terms. We mainly focus on theories containing only the Ricci tensor and show the crucial role played by the projective symmetry. The pathological modes arise from the absence of a pure kinetic term for the projective mode and the non-minimal coupling of a 2-form field contained in the connection, and which can be related to the antisymmetric part of the metric in non-symmetric gravity theories. The couplings to matter are considered at length and cannot be used to render the theories stable. We discuss different procedures to avoid the ghosts by adding additional constraints. We finally argue how these pathologies are expected to be present in general metric-affine theories unless much care is taken in their construction.
