Torsion talks only to spin: the CMB temperature as a test of energy exchange in Einstein-Cartan cosmology
Abstract
The cosmic microwave background temperature at z=0.886 is known to 2% from molecular absorption towards PKS~1830−211; CO absorbers and Sunyaev-Zel'dovich clusters extend the measurement to z≃3. We use them on a question that cosmologies with torsion leave open. When the geometry exchanges energy with several matter components, which of them receives it? In Einstein-Cartan theory the Noether identities of each sector fix the answer. A sector's energy-momentum fails to be conserved only in proportion to its own spin, so minimally coupled light, which has none, is conserved whatever the torsion does. A metric-affine cosmology fitted to DESI DR2 distributes the exchange ``universally'' among all fluids, radiation included; the photons then gain almost a third of their energy. If the photons stay a blackbody, as FIRAS requires of any source set by local conditions, the model predicts a background colder than T0(1+z) by 7% at z≃0.9 and by 8.5% at z≳3, with no free parameter. PKS~1830−211 gives 5.08±0.10 K against a predicted 4.78 K; with the CO absorbers it favours the standard scaling by Δχ2=13, and 18 Planck cluster bins give χ2=50.8 versus $15.5$. Under the same reading the primary anisotropies would change their spectral shape by amounts Planck excludes. If dark matter carries the spin instead, H(z) moves by less than 10−4 below z=3 at the fitted parameters and T(z) is standard again.
Related
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BibTeX
@misc{izaurieta2026torsion,
title = {{Torsion talks only to spin: the CMB temperature as a test of energy exchange in Einstein-Cartan cosmology}},
author = {Fernando Izaurieta and Samuel Lepe and Cristian Quinzacara},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.08422},
eprint = {2611.08422},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.08422},
}
RIS
TY - UNPB
TI - Torsion talks only to spin: the CMB temperature as a test of energy exchange in Einstein-Cartan cosmology
AU - Fernando Izaurieta
AU - Samuel Lepe
AU - Cristian Quinzacara
PY - 2026
DA - 2026/11/05
PB - arXiv
DO - 10.48550/arxiv.2611.08422
UR - https://arxiv.org/abs/2611.08422
AB - The cosmic microwave background temperature at z=0.886 is known to 2% from molecular absorption towards PKS~1830−211; CO absorbers and Sunyaev-Zel'dovich clusters extend the measurement to z≃3. We use them on a question that cosmologies with torsion leave open. When the geometry exchanges energy with several matter components, which of them receives it? In Einstein-Cartan theory the Noether identities of each sector fix the answer. A sector's energy-momentum fails to be conserved only in proportion to its own spin, so minimally coupled light, which has none, is conserved whatever the torsion does. A metric-affine cosmology fitted to DESI DR2 distributes the exchange ``universally'' among all fluids, radiation included; the photons then gain almost a third of their energy. If the photons stay a blackbody, as FIRAS requires of any source set by local conditions, the model predicts a background colder than T_0(1+z) by 7% at z≃0.9 and by 8.5% at z≳3, with no free parameter. PKS~1830−211 gives 5.08±0.10 K against a predicted 4.78 K; with the CO absorbers it favours the standard scaling by Δχ^2=13, and 18 Planck cluster bins give χ^2=50.8 versus $15.5$. Under the same reading the primary anisotropies would change their spectral shape by amounts Planck excludes. If dark matter carries the spin instead, H(z) moves by less than 10^−4 below z=3 at the fitted parameters and T(z) is standard again.
ER -