`Positivity Bounds in Effective Field Theories of Gravity'

该项目将探索有效量子场论的最新理论发展，其中20世纪60年代的s矩阵程序工具已被证明为低能量有效场论的一致性提供了强有力的约束，特别是可以描述宇宙膨胀的暴胀或暗能量阶段的宇宙学有效场论。这些约束来自于一个一致的洛伦兹不变量子理论必须满足统一性、交叉对称性、局部性和因果性的首要要求。在帝国理工学院理论物理小组最近的工作中，这些要求已经被证明在有效的场论扩展中对参数施加了无限数量的界限，这些界限可以用来积极地约束引力和宇宙学模型的候选理论。特别是，这些约束已经被用来极大地约束质量引力理论的参数空间，这些理论被认为是具有解决宇宙常数潜力的宇宙尺度引力的候选理论。该项目将继续这一探索，并对多重自旋2和更高场的理论施加约束。

The project will explore the very recent theoretical developments in effective quantum field theories, in which the tools of the S-matrix program of the 1960's have been shown to provide powerful constraints on the consistency of low energy effective field theories, in particular cosmological effective field theories that can describe the inflationary or dark energy phases of expansion of the universe. These constraints arise from the overarching requirements that a consistent Lorentz invariant quantum theory should satisfy unitarity, crossing symmetry, locality and causality. In recent work within the theoretical physics group at Imperial College, these requirements have been shown to impose an infinite number of bounds on the parameters in an effective field theory expansion that can be used to actively constrain candidate theories of gravity and cosmological models. In particular these constraints are already being used to significantly constrain the parameter space of massive gravity theories, which have been considered as candidate theories of gravity at cosmological scales with the potential to tackle the cosmological constant. The project will continue this exploration and put constraints on theories of multiple spin 2 and higher fields.