Twin Universes and Bimetric Gravity: From Sakharov's Cosmological Symmetry to Modern Speculations on Negative Mass
Abstract
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.
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BibTeX
@misc{luminet2026twin,
title = {{Twin Universes and Bimetric Gravity: From Sakharov's Cosmological Symmetry to Modern Speculations on Negative Mass}},
author = {Jean-Pierre Luminet},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.26834},
eprint = {2609.26834},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.26834},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Twin Universes and Bimetric Gravity: From Sakharov's Cosmological Symmetry to Modern Speculations on Negative Mass
AU - Jean-Pierre Luminet
PY - 2026
DA - 2026/10/02
PB - arXiv
DO - 10.48550/arxiv.2609.26834
UR - https://arxiv.org/abs/2609.26834
AB - 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.
ER -