The relevance of the cosmic microwave background for cosmology
Abstract
Within the Hot Big Bang picture, as usually interpreted in the standard LCDM framework and its hierarchical scenario for elliptical galaxy assembly, the cosmic microwave background (CMB) is associated with photon decoupling near z = 1100, and the Planck angular power spectra are taken to constrain primordial 10^{-5}-level fluctuations that seeded later structure formation. We show that, in addition to the LCDM model, two cosmological models based on Milgromian gravitation are also consistent with the Planck CMB power spectra, such that the spectra do not uniquely favor dark matter. We then argue that the published CMB spectra are not direct observables, but reconstructed quantities obtained after foreground subtraction and corrections for weak lensing, photon-electron scattering, and gravitational energy redshifts along the line of sight. Because these steps depend on the assumed growth history of structure, the resulting spectra depend on the cosmological model adopted in the data reduction. We also note that the reported correlation between the hemispherical CMB asymmetry and the excess on-sky distribution of elliptical galaxies may point to matter inhomogeneities spanning large portions of the observable universe. Motivated by observational tensions in the hierarchical assembly of elliptical galaxies, we review the consequences of elliptical-galaxy formation on a downsizing timescale, which implies a significant extragalactic foreground released at 15< z < 20. Under conservative assumptions, this foreground contributes at least 1.4 percent of the observed CMB energy density and has not been included in CMB analyses. It follows that the reported 10^{-5}-level fluctuations is introduced by overly aggressive foreground cleaning.
Versions
Related
- A consistent, physical, and analytical model for cosmic microwave background observables of reionisation. I. Derivation, constraining power, and detectability of the auto spectra
- 2% determination of N eff from primordial element abundance, cosmic microwave background, and baryon acoustic oscillation measurements
- Atmosphere mitigation in cosmic microwave background observations using multifrequency time-domain component separation
- Optimization of multi-resolution observation strategies for cosmic microwave background experiments
- Unveiling the Dark Ages: A New Pathway Using Tomographical 21 cm Cosmic Microwave Background Cross-correlations
BibTeX
@misc{kroupa2026relevance,
title = {{The relevance of the cosmic microwave background for cosmology}},
author = {Pavel Kroupa and Eda Gjergo and Nikolaos Samaras},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.10672},
eprint = {2609.10672},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.10672},
}
RIS
TY - UNPB
TI - The relevance of the cosmic microwave background for cosmology
AU - Pavel Kroupa
AU - Eda Gjergo
AU - Nikolaos Samaras
PY - 2026
DA - 2026/09/09
PB - arXiv
DO - 10.48550/arxiv.2609.10672
UR - https://arxiv.org/abs/2609.10672
AB - Within the Hot Big Bang picture, as usually interpreted in the standard LCDM framework and its hierarchical scenario for elliptical galaxy assembly, the cosmic microwave background (CMB) is associated with photon decoupling near z = 1100, and the Planck angular power spectra are taken to constrain primordial 10^{-5}-level fluctuations that seeded later structure formation. We show that, in addition to the LCDM model, two cosmological models based on Milgromian gravitation are also consistent with the Planck CMB power spectra, such that the spectra do not uniquely favor dark matter. We then argue that the published CMB spectra are not direct observables, but reconstructed quantities obtained after foreground subtraction and corrections for weak lensing, photon-electron scattering, and gravitational energy redshifts along the line of sight. Because these steps depend on the assumed growth history of structure, the resulting spectra depend on the cosmological model adopted in the data reduction. We also note that the reported correlation between the hemispherical CMB asymmetry and the excess on-sky distribution of elliptical galaxies may point to matter inhomogeneities spanning large portions of the observable universe. Motivated by observational tensions in the hierarchical assembly of elliptical galaxies, we review the consequences of elliptical-galaxy formation on a downsizing timescale, which implies a significant extragalactic foreground released at 15< z < 20. Under conservative assumptions, this foreground contributes at least 1.4 percent of the observed CMB energy density and has not been included in CMB analyses. It follows that the reported 10^{-5}-level fluctuations is introduced by overly aggressive foreground cleaning.
ER -