Growth, geometry, and early-universe split of the matter density parameter Ωm
Abstract
While the Λ cold dark matter (ΛCDM) model can successfully reproduce the measurements of many cosmological probes, some discrepancies have recently emerged. It is therefore necessary to test the standard cosmological model for consistency. An important stress test is to separate the effect of different cosmological regimes on the parameter inference. We treat three regimes separately here: geometry, growth, and the early Universe. The geometric regime concerns the expansion and curvature history, the growth regime governs structure formation, and the early-universe regime affects physics prior to recombination. Previous analyses have performed the split between geometry and growth, whereas we also consider the influence of the early Universe separately. We performed this split for the present-day matter density parameter Ωm using multiple cosmological observables. The data we used are galaxy clustering and weak-lensing statistics (3x2pt) from the Dark Energy Survey, cosmic microwave background data from Planck, baryon acoustic oscillations from the Dark Energy Spectroscopic Instrument, type Ia supernovae samples from Pantheon+, and redshift-space distortions from a collection of galaxy surveys. For each of these probes, we introduced a phenomenological split into these three regimes. The correlation between the geometric and the early regime for the matter density is strong, but that between the growth regime and the others is not. All regimes are compatible in the posterior distribution, but the difference between the geometry and the early regimes, ΔΩmgeo,early, has a 2σ discrepancy with 0.
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BibTeX
@misc{keil2026growth,
title = {{Growth, geometry, and early-universe split of the matter density parameter $Ω_\rm m$}},
author = {Felicitas Keil and Isaac Tutusaus and Alain Blanchard},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.28326},
eprint = {2607.28326},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.28326},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Growth, geometry, and early-universe split of the matter density parameter Ω_m
AU - Felicitas Keil
AU - Isaac Tutusaus
AU - Alain Blanchard
PY - 2026
DA - 2026/10/07
PB - arXiv
DO - 10.48550/arxiv.2607.28326
UR - https://arxiv.org/abs/2607.28326
AB - While the Λ cold dark matter (ΛCDM) model can successfully reproduce the measurements of many cosmological probes, some discrepancies have recently emerged. It is therefore necessary to test the standard cosmological model for consistency. An important stress test is to separate the effect of different cosmological regimes on the parameter inference. We treat three regimes separately here: geometry, growth, and the early Universe. The geometric regime concerns the expansion and curvature history, the growth regime governs structure formation, and the early-universe regime affects physics prior to recombination. Previous analyses have performed the split between geometry and growth, whereas we also consider the influence of the early Universe separately. We performed this split for the present-day matter density parameter Ω_m using multiple cosmological observables. The data we used are galaxy clustering and weak-lensing statistics (3x2pt) from the Dark Energy Survey, cosmic microwave background data from Planck, baryon acoustic oscillations from the Dark Energy Spectroscopic Instrument, type Ia supernovae samples from Pantheon+, and redshift-space distortions from a collection of galaxy surveys. For each of these probes, we introduced a phenomenological split into these three regimes. The correlation between the geometric and the early regime for the matter density is strong, but that between the growth regime and the others is not. All regimes are compatible in the posterior distribution, but the difference between the geometry and the early regimes, ΔΩ_m^geo,early, has a 2σ discrepancy with 0.
ER -