标题： 关于标量-轴子引力的宇宙学和对称性 显示英文标题

标题： On the Cosmology and Symmetry of Dilaton-Axion Gravity

摘要： 一个全局的O$(2,2)$对称性在标量-张量引力理论中被发现，当膨胀子与轴子和模场耦合时。如果引入宇宙学常数，该对称性会被破坏。在空间齐次的Bianchi宇宙模型中，只有I型和V型模型尊重该对称性。对于任意的空间曲率，找到了各向同性的宇宙学解。在与预大爆炸场景相关的参数空间区域，标量场之间的相互作用导致了宇宙反弹。 显示英文摘要

摘要： A global O$(2,2)$ symmetry is found in the Brans-Dicke theory of gravity when the dilaton is coupled to axion and moduli fields. The symmetry is broken if a cosmological constant is introduced. Within the class of spatially homogeneous Bianchi cosmologies, only the type I and V models respect the symmetry. Isotropic cosmological solutions are found for arbitrary spatial curvature. In the region of parameter space relevant to the pre-big bang scenario, the interplay between the scalar fields results in a bouncing cosmology.