Glavan Dražen, Lin Chunshan
Centre for Cosmology, Particle Physics and Phenomenology (CP3), Université catholique de Louvain, Chemin du Cyclotron 2, 1348 Louvain-la-Neuve, Belgium.
Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland.
Phys Rev Lett. 2020 Feb 28;124(8):081301. doi: 10.1103/PhysRevLett.124.081301.
In this Letter we present a general covariant modified theory of gravity in D=4 spacetime dimensions which propagates only the massless graviton and bypasses Lovelock's theorem. The theory we present is formulated in D>4 dimensions and its action consists of the Einstein-Hilbert term with a cosmological constant, and the Gauss-Bonnet term multiplied by a factor 1/(D-4). The four-dimensional theory is defined as the limit D→4. In this singular limit the Gauss-Bonnet invariant gives rise to nontrivial contributions to gravitational dynamics, while preserving the number of graviton degrees of freedom and being free from Ostrogradsky instability. We report several appealing new predictions of this theory, including the corrections to the dispersion relation of cosmological tensor and scalar modes, singularity resolution for spherically symmetric solutions, and others.
在这封信中，我们提出了一种在四维时空维度下的广义协变修正引力理论，该理论仅传播无质量引力子并绕过了洛夫洛克定理。我们提出的理论是在大于四维的维度中表述的，其作用量由带有宇宙学常数的爱因斯坦 - 希尔伯特项以及乘以因子1 /(D - 4) 的高斯 - 博内项组成。四维理论定义为D趋于4的极限。在这个奇异极限下，高斯 - 博内不变量对引力动力学产生非平凡贡献，同时保持引力子自由度的数量且不存在奥斯特罗格拉德斯基不稳定性。我们报告了该理论的几个引人注目的新预测，包括对宇宙学张量和标量模式色散关系的修正、球对称解的奇点解析等。
