孪生宇宙与双度量引力：从萨哈罗夫的宇宙学对称性到关于负质量的现代猜想
Twin Universes and Bimetric Gravity: From Sakharov's Cosmological Symmetry to Modern Speculations on Negative Mass
- Laboratoire d’Astrophysique de Marseille (LAM), Centre National de la Recherche Scientifique, Aix-Marseille Université（马赛天体物理学实验室（LAM），法国国家科学研究中心，艾克斯-马赛大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文综述孪生宇宙模型，从萨哈罗夫对称性到双度量引力与负质量猜想，指出其面临鬼场、一致性条件及观测验证等重大挑战。
AI中文摘要：
我们回顾了孪生宇宙模型的概念和理论地位，从萨哈罗夫关于重子生成、CPT对称性和时间箭头反转的早期思想，到涉及成对创生的纠缠宇宙的近期量子宇宙学情景。特别关注萨哈罗夫型宇宙学对称性、现代双度量引力理论以及涉及负质量扇区的推测性模型之间的区别。我们总结了双度量引力面临的主要一致性条件，包括Boulware-Deser鬼场、Higuchi型界限、协变守恒定律以及针对正质量和负质量扇区的不可行性结果。然后，我们考察了Janus宇宙学模型和相关的黑洞替代提议，强调了启发式孪生宇宙叙事与完全明确的相对论场论之间的区别。我们认为，虽然孪生宇宙思想仍然是探讨时间箭头、物质-反物质不对称性和宇宙量子起源等问题的丰富框架，但结合双度量引力、负质量、暗扇区现象学以及克尔黑洞替代方案的模型，面临着实质性的数学和观测证明负担。
英文摘要：
We review the conceptual and theoretical status of twin-universe models, from Sakharov's early ideas on baryogenesis, CPT symmetry, and reversed arrows of time to recent quantum-cosmological scenarios involving pair-created entangled universes. Particular attention is given to the distinction between Sakharov-type cosmological symmetry, modern bimetric theories of gravity, and speculative models involving negative mass sectors. We summarize the main consistency conditions faced by bimetric gravity, including the Boulware-Deser ghost, Higuchi-type bounds, covariant conservation laws, and no-go results for positive- and negative-mass sectors. We then examine the Janus cosmological model and related black-hole replacement proposals, emphasizing the difference between heuristic twin-universe narratives and fully specified relativistic field theories. We argue that while twin-universe ideas remain a fertile framework for questions about the arrow of time, matter-antimatter asymmetry, and the quantum origin of the universe, models combining bimetric gravity, negative mass, dark-sector phenomenology, and alternatives to Kerr black holes face a substantial burden of mathematical and observational proof.
