CF4 data yield a 3.3σ excess dipole in the local expansion-rate fluctuation field at (l,b)=(290°,-4°)±5°, sourced mainly by z∈[0.03,0.05], with quadrupole/octupole consistent with ΛCDM and no multipole-vector alignments.
Kumar Aluri, P
11 Pith papers cite this work. Polarity classification is still indexing.
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abstract
The Cosmological Principle (CP) -- the notion that the Universe is spatially isotropic and homogeneous on large scales -- underlies a century of progress in cosmology. It is conventionally formulated through the Friedmann-Lema\^itre-Robertson-Walker (FLRW) cosmologies as the spacetime metric, and culminates in the successful and highly predictive $\Lambda$-Cold-Dark-Matter ($\Lambda$CDM) model. Yet, tensions have emerged within the $\Lambda$CDM model, most notably a statistically significant discrepancy in the value of the Hubble constant, $H_0$. Since the notion of cosmic expansion determined by a single parameter is intimately tied to the CP, implications of the $H_0$ tension may extend beyond $\Lambda$CDM to the CP itself. This review surveys current observational hints for deviations from the expectations of the CP, highlighting synergies and disagreements that warrant further study. Setting aside the debate about individual large structures, potential deviations from the CP include variations of cosmological parameters on the sky, discrepancies in the cosmic dipoles, and mysterious alignments in quasar polarizations and galaxy spins. While it is possible that a host of observational systematics are impacting results, it is equally plausible that precision cosmology may have outgrown the FLRW paradigm, an extremely pragmatic but non-fundamental symmetry assumption.
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DESI recovers the CMB-constrained parameter combination at sub-percent precision; high-redshift DES supernovae fit flat Lambda CDM while a 0.05 mag offset in the low-redshift anchor sample may be systematic, supporting overall model consistency from recombination to the local universe.
A divide-and-conquer framework using QAOA and neural network surrogates accelerates constrained MCMC by factors of 7.6 to 20.3 over classical methods.
Inhomogeneous decelerating models generate effective accelerating FLRW universes at large scales through backreaction that mimics a running dark-energy term.
Bin-wise uncorrelated reconstruction from DESI/SDSS BAO and Pantheon+/Union3.1/DES-Dovekie supernovae yields dark energy density peaking then declining and equation of state oscillating with phantom crossing near z~0.7, consistent across datasets at moderate significance.
A multi-bin simultaneous dipole fitting method yields higher Bayes factors than single flux-cut approaches for non-power-law luminosity functions in cosmic dipole measurements.
Numerical simulations show that inhomogeneities in a LambdaCDM universe can lead some observers to infer evolving dark energy parameters consistent with DESI at 2-sigma.
Analysis of galaxy cluster and supernova data reveals a ~2σ directional variation in the Hubble constant, robust across calibration methods and aligned with the CMB dipole.
Local Hubble constant anisotropy in Cosmicflows-4 data is primarily attributed to peculiar velocities and survey structure rather than cosmic-scale isotropy violation, with limited implications for the Hubble tension.
N-body simulations show that peculiar velocities produce large dispersion in local H0 estimates at scales below ~135 Mpc/h, with >5% deviations common up to 40 Mpc/h and a negative correlation with local over-density.
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Multipolar structure of the local expansion rate from incomplete sky data
CF4 data yield a 3.3σ excess dipole in the local expansion-rate fluctuation field at (l,b)=(290°,-4°)±5°, sourced mainly by z∈[0.03,0.05], with quadrupole/octupole consistent with ΛCDM and no multipole-vector alignments.
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Consistency of DES and DESI distances and the Standard Cosmological Model
DESI recovers the CMB-constrained parameter combination at sub-percent precision; high-redshift DES supernovae fit flat Lambda CDM while a 0.05 mag offset in the low-redshift anchor sample may be systematic, supporting overall model consistency from recombination to the local universe.
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Forecasts of CMB $E$-mode anomalies for AliCPT-1
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A class of decelerating inhomogeneous cosmological models giving rise to accelerating FLRW universes at large scales
Inhomogeneous decelerating models generate effective accelerating FLRW universes at large scales through backreaction that mimics a running dark-energy term.
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Reconstructing dark energy with fewer assumptions
Bin-wise uncorrelated reconstruction from DESI/SDSS BAO and Pantheon+/Union3.1/DES-Dovekie supernovae yields dark energy density peaking then declining and equation of state oscillating with phantom crossing near z~0.7, consistent across datasets at moderate significance.
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The Ellis and Baldwin test of the Cosmic Dipole: Exploring the impact of multiple flux density cuts
A multi-bin simultaneous dipole fitting method yields higher Bayes factors than single flux-cut approaches for non-power-law luminosity functions in cosmic dipole measurements.
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Numerical simulations show that inhomogeneities in a LambdaCDM universe can lead some observers to infer evolving dark energy parameters consistent with DESI at 2-sigma.
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Probing cosmic anisotropy with galaxy clusters and supernovae
Analysis of galaxy cluster and supernova data reveals a ~2σ directional variation in the Hubble constant, robust across calibration methods and aligned with the CMB dipole.
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Updates on dipolar anisotropy in local measurements of the Hubble constant from Cosmicflows-4
Local Hubble constant anisotropy in Cosmicflows-4 data is primarily attributed to peculiar velocities and survey structure rather than cosmic-scale isotropy violation, with limited implications for the Hubble tension.
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Dispersion in the Hubble-Lema\^{i}tre constant measurements from gravitational clustering
N-body simulations show that peculiar velocities produce large dispersion in local H0 estimates at scales below ~135 Mpc/h, with >5% deviations common up to 40 Mpc/h and a negative correlation with local over-density.
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