A Z_N-symmetric multi-copy dark-QCD axion, broken by single-sector reheating, yields natural phantom-crossing dark energy with dark-pion DM in a viable parameter window.
Joint analysis of 6dFGS and SDSS peculiar velocities for the growth rate of cosmic structure and tests of gravity
6 Pith papers cite this work. Polarity classification is still indexing.
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Pith papers citing it
abstract
Measurement of peculiar velocities by combining redshifts and distance indicators is a powerful way to measure the growth rate of cosmic structure and test theories of gravity at low redshift. Here we constrain the growth rate of structure by comparing observed Fundamental Plane peculiar velocities for 15894 galaxies from the 6dF Galaxy Survey (6dFGS) and Sloan Digital Sky Survey (SDSS) with predicted velocities and densities from the 2M$++$ redshift survey. We measure the velocity scale parameter $\beta \equiv {\Omega_m^\gamma}/b = 0.372^{+0.034}_{-0.050}$ and $0.314^{+0.031}_{-0.047}$ for 6dFGS and SDSS respectively, where $\Omega_m$ is the mass density parameter, $\gamma$ is the growth index, and $b$ is the bias parameter normalized to the characteristic luminosity of galaxies, $L^*$. Combining 6dFGS and SDSS we obtain $\beta= 0.341\pm0.024$, implying that the amplitude of the product of the growth rate and the mass fluctuation amplitude is $f\sigma_8 = 0.338\pm0.027$ at an effective redshift $z=0.035$. Adopting $\Omega_m = 0.315\pm0.007$ as favoured by Planck and using $\gamma=6/11$ for General Relativity and $\gamma=11/16$ for DGP gravity, we get $S_8(z=0) = \sigma_8 \sqrt{\Omega_m/0.3} =0.637 \pm 0.054$ and $0.741\pm0.062$ for GR and DGP respectively. This measurement agrees with other low-redshift probes of large scale structure but deviates by more than $3\sigma$ from the latest Planck CMB measurement. Our results favour values of the growth index $\gamma > 6/11$ or a Hubble constant $H_0 > 70$\,km\,s$^{-1}$\,Mpc$^{-1}$ or a fluctuation amplitude $\sigma_8 < 0.8$ or some combination of these. Imminent redshift surveys such as Taipan, DESI, WALLABY, and SKA1-MID will help to resolve this tension by measuring the growth rate of cosmic structure to 1\% in the redshift range $0 < z < 1$.
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representative citing papers
Combining gravitational-potential decay-rate (DR) data with Σ8 and fσ8 growth measurements tightens modified-gravity parameter constraints by ~1.5–2×, with all results consistent with general relativity.
Using Planck, DESI, supernovae, and redshift-space distortions, the authors infer that modified gravity, if present, must act only below ~30 Mpc and cannot modify the large scales previously considered.
DESI DR1 peculiar velocity data yields fσ8(z_eff=0.07) = 0.450 ± 0.055, consistent with Planck ΛCDM and GR growth index γ = 0.58 ± 0.11.
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.
Transformer and GBDT models trained on AbacusSummit mocks for DESI LRGs/ELGs recover nonlinear velocity power spectra and cross-correlations better than linear theory across a wider range of scales, with applications to kSZ analyses.
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Natural Phantom Dark Energy from a $\mathbb{Z}_N$--Axion
A Z_N-symmetric multi-copy dark-QCD axion, broken by single-sector reheating, yields natural phantom-crossing dark energy with dark-pion DM in a viable parameter window.
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Synergy between the gravitational potential decay rate and other structure growth probes in testing gravity
Combining gravitational-potential decay-rate (DR) data with Σ8 and fσ8 growth measurements tightens modified-gravity parameter constraints by ~1.5–2×, with all results consistent with general relativity.
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Signatures of Modified Gravity on Linear Scales in a Dynamical Dark Energy Background
Using Planck, DESI, supernovae, and redshift-space distortions, the authors infer that modified gravity, if present, must act only below ~30 Mpc and cannot modify the large scales previously considered.
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The DESI DR1 Peculiar Velocity Survey: growth rate measurements from the maximum likelihood fields method
DESI DR1 peculiar velocity data yields fσ8(z_eff=0.07) = 0.450 ± 0.055, consistent with Planck ΛCDM and GR growth index γ = 0.58 ± 0.11.
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On the potential for inhomogeneities to mimic an evolving dark energy
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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Full Nonlinear Velocity Reconstruction With Transformer and Ensemble Tree Machine Learning
Transformer and GBDT models trained on AbacusSummit mocks for DESI LRGs/ELGs recover nonlinear velocity power spectra and cross-correlations better than linear theory across a wider range of scales, with applications to kSZ analyses.