Effective Neutrino Mass and Apparent Phantom Crossing
Abstract
Recent cosmological constraints on the sum of neutrino masses have reached, and in some analyses fallen below, the minimum value implied by the normal mass ordering, suggesting a possible tension with neutrino-oscillation measurements. We investigate whether this discrepancy can be alleviated in a mass-varying-neutrino (MaVaN) cosmology in which a canonical pseudo-Nambu-Goldstone boson (pNGB) drives late-time cosmic acceleration and controls the masses of massive neutrinos through an exponential coupling. Using current cosmic microwave background, baryon acoustic oscillation, and type Ia supernova data, we reconstruct the neutrino-mass evolution and show that the cosmologically inferred effective neutrino mass can fall below the present-day normal-ordering floor while remaining consistent with oscillation constraints. The same interaction produces a distinctive late-time signature, with 96% of the posterior expansion histories exhibiting a crossing of the apparent phantom divide, wapp=−1, at zcross=0.90+0.28−0.13 at 68% C.L. The underlying scalar field nevertheless remains canonical, with wϕ≥ −1. Our results therefore show that neutrino mass variation can simultaneously alleviate the apparent neutrino-mass tension and generate the phantom-crossing behavior favored by current cosmological data, without introducing a phantom field or violating the null energy condition.
Related
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BibTeX
@misc{rodrigues2026effective,
title = {{Effective Neutrino Mass and Apparent Phantom Crossing}},
author = {Gabriel Rodrigues and Jamerson Rodrigues and Simony Santos da Costa and Jailson Alcaniz},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.10195},
eprint = {2610.10195},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.10195},
}
RIS
TY - UNPB
TI - Effective Neutrino Mass and Apparent Phantom Crossing
AU - Gabriel Rodrigues
AU - Jamerson Rodrigues
AU - Simony Santos da Costa
AU - Jailson Alcaniz
PY - 2026
DA - 2026/10/11
PB - arXiv
DO - 10.48550/arxiv.2610.10195
UR - https://arxiv.org/abs/2610.10195
AB - Recent cosmological constraints on the sum of neutrino masses have reached, and in some analyses fallen below, the minimum value implied by the normal mass ordering, suggesting a possible tension with neutrino-oscillation measurements. We investigate whether this discrepancy can be alleviated in a mass-varying-neutrino (MaVaN) cosmology in which a canonical pseudo-Nambu-Goldstone boson (pNGB) drives late-time cosmic acceleration and controls the masses of massive neutrinos through an exponential coupling. Using current cosmic microwave background, baryon acoustic oscillation, and type Ia supernova data, we reconstruct the neutrino-mass evolution and show that the cosmologically inferred effective neutrino mass can fall below the present-day normal-ordering floor while remaining consistent with oscillation constraints. The same interaction produces a distinctive late-time signature, with 96% of the posterior expansion histories exhibiting a crossing of the apparent phantom divide, w_app=−1, at z_cross=0.90^+0.28_−0.13 at 68% C.L. The underlying scalar field nevertheless remains canonical, with w_ϕ≥ −1. Our results therefore show that neutrino mass variation can simultaneously alleviate the apparent neutrino-mass tension and generate the phantom-crossing behavior favored by current cosmological data, without introducing a phantom field or violating the null energy condition.
ER -