Gravity can be regarded as a consequence of local Lorentz (LL) symmetry, which is essential in defining a spinor field in curved spacetime. The gravitational action may admit a zero-field limit of the metric and vierbein at a certain ultraviolet cutoff scale such that the action becomes a linear realization of the LL symmetry. Consequently, only three types of term are allowed in the four-dimensional gravitational action at the cutoff scale: a cosmological constant, a linear term of the LL field strength, and spinor kinetic terms, whose coefficients are in general arbitrary functions of LL and diffeomorphism invariants. In particular, all the kinetic terms are prohibited except for spinor fields, and hence the other fields are auxiliary. Their kinetic terms, including those of the LL gauge field and the vierbein, are induced by spinor loops simultaneously with the LL gauge field mass. The LL symmetry is necessarily broken spontaneously and hence is nothing but a hidden local symmetry, from which gravity is emergent.

中文翻译：

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来自隐藏的局部洛伦兹对称性的动态涌现重力

重力可以被视为局部洛伦兹 (LL) 对称性的结果，这对于定义弯曲时空中的自旋场至关重要。引力作用可以在一定的紫外线截止尺度上允许度量和 vierbein 的零场限制，从而使该作用成为 LL 对称性的线性实现。因此，在截止尺度的四维引力作用中只允许三种类型的项：宇宙常数、LL 场强的线性项和旋量动力学项，其系数通常是 LL 和微分同胚的任意函数不变量。特别是，除自旋场外的所有动力学项都被禁止，因此其他场是辅助场。它们的动力学项，包括 LL 规范场和 vierbein 的那些项，由自旋环与 LL 规范场质量同时引起。LL 对称性必然会自发地破缺，因此它只不过是一种隐藏的局部对称性，引力由此而生。