Citation

BibTex format

@article{Hallam:2026:09/039,
author = {Hallam, J and Magueijo, J},
doi = {09/039},
journal = {Journal of Cosmology and Astroparticle Physics},
pages = {039--039},
title = {Bimodular gravity: vacuum evolution with a frame-dependent phantom crossing},
url = {http://dx.doi.org/10.1088/1475-7516/2026/09/039},
volume = {2026},
year = {2026}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - <jats:title>Abstract</jats:title>                  <jats:p>Unimodular gravity recasts the cosmological constant as an integration constant, fixed by a constraint on the volume element rather than chosen in the action. We ask what becomes of this constant when matter couples not to the gravitational metric, but to a second metric disformally related to it through a scalar field. Imposing a volume constraint on each metric, we find a theory in which the scalar does not propagate, yet still drives a non-trivial expansion. Written as a single-metric theory, its kinetic term is fixed to a prescribed function of spacetime, and the cosmological constant is replaced by a vacuum contribution that need not be constant. Moreover, we find that this theory admits a phantom crossing through a purely frame-dependent mechanism. This construction, however, rests on a feature invisible with a single metric, and unimodular formalisms that are classically equivalent in that case cease to agree once there are two disformally related metrics.</jats:p>
AU  - Hallam,J
AU  - Magueijo,J
DO  - 09/039
EP  - 039
PY  - 2026///
SP  - 039
TI  - Bimodular gravity: vacuum evolution with a frame-dependent phantom crossing
T2  - Journal of Cosmology and Astroparticle Physics
UR  - http://dx.doi.org/10.1088/1475-7516/2026/09/039
UR  - https://doi.org/10.1088/1475-7516/2026/09/039
VL  - 2026
ER  -
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