## 物理学：引力的修改理论图解

对引力的修改理论，下图基本上囊括了主要的一些路线。

While Einstein’s general relativity has been well tested by various observations, it is possible that at the cosmological scale it might require some modification or extension, which could, in turn, explain dark matter or dark energy. There exist a plethora of modified theories of gravity, from simple straightforward generalizations of the Hilbert-Einstein action (e.g. f(R) gravity), to utilizing other geometric structures (e.g. f(T) gravity that models gravity as spacetime torsion instead of curvature), it is important to constrain these theories from both observations and theoretical grounds (a good theory should be mathematically self-consistent and free of pathologies). [Figure source: Tessa Baker]