标题： 度规仿射引力中来自扩展射影对称性的协调粒子物理 显示英文标题

标题： Consistent particle physics in metric-affine gravity from extended projective symmetry

摘要： 众所周知，爱因斯坦-希尔伯特作用量在度规仿射引力中表现出一种由单个矢量生成的投影不变性（就像微分同胚一样）。 然而，这种对称性并不能防止构造不一致的模型，例如存在鬼态和强耦合问题的模型。 在本文中，我们观察到狄拉克旋量的非最小动力项指向一种由一对矢量生成的新扩展投影（EP）对称性。 我们证明，最一般的EP不变理论（场强最多二次）自然地避免了所有病态。 其谱仅包含无质量的引力子和一个额外的标量场，该标量场来源于霍尔斯特曲率的平方。 标量势适合于暴胀，我们的模型还包含有效的四费米子相互作用，能够产生费米型暗物质。 最后，我们指出另一种双矢量对称性，它同样导致一个具有传播矢量场的健康理论。 显示英文摘要

摘要： It is well-known that the Einstein-Hilbert action exhibits a projective invariance in metric-affine gravity, generated by a single vector (just like diffeomorphisms). However, this symmetry offers no protection against formulating inconsistent models, e.g., with ghost and strong coupling problems. In this letter, we observe that non-minimal kinetic terms of Dirac spinors point to a new extended projective (EP) symmetry generated by a pair of vectors. We prove that the most general EP-invariant theory (at most quadratic in field strengths) is naturally free from all pathologies. Its spectrum only features the massless graviton and a single additional scalar field arising from the square of the Holst curvature. The scalar potential is suitable for inflation and our model moreover contains effective 4-Fermi interactions capable of producing fermionic dark matter. Finally, we point out an alternative double-vector symmetry that similarly leads to a healthy theory with a propagating vector field.