Eur. Phys. J. C 80, 1079 (2020) arXiv link
Cosmological time crystals from Einstein-cubic gravities
Xing-Hui Feng1, Hyat Huang2, Shou-Long Li1,3,4,*, H. Lü1 & Hao Wei4
1 Center for Joint Quantum Studies and Department of Physics, School of Science, Tianjin University, Tianjin, 300350, China
2 College of Physics and Communication Electronics, Jiangxi Normal University, Nanchang, 330022, China
3 Department of Physics and Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, 410081, Hunan, China
4 School of Physics, Beijing Institute of Technology, Beijing, 100081, China
* shoulongli@hunnu.edu.cn
Abstract
By including appropriate Riemann-cubic invariants, we find that the dynamics of classical time crystals can be straightforwardly realized in Einstein gravity on the FLRW metric. The time reflection symmetry is spontaneously broken in the two vacua with the same scale factor a, but opposite
a˙
. The tunneling from one vacuum to the other provides a robust mechanism for bounce universes; it always occurs for systems with positive energy density. For a suitable matter energy-momentum tensor we also construct cyclic universes. Cosmological solutions that resemble the classical time crystals can be constructed in massive gravity.
