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.
Testing $\Lambda$CDM at the lowest redshifts with SN Ia and galaxy velocities
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abstract
Peculiar velocities of objects in the nearby universe are correlated due to the gravitational pull of large-scale structure. By measuring these velocities, we have a unique opportunity to test the cosmological model at the lowest redshifts. We perform this test, using current data to constrain the amplitude of the "signal" covariance matrix describing the velocities and their correlations. We consider a new, well-calibrated "Supercal" set of low-redshift SNe Ia as well as a set of distances derived from the fundamental plane relation of 6dFGS galaxies. Analyzing the SN and galaxy data separately, both results are consistent with the peculiar velocity signal of our fiducial $\Lambda$CDM model, ruling out the noise-only model with zero peculiar velocities at greater than $7\sigma$ (SNe) and $8\sigma$ (galaxies). When the two data sets are combined appropriately, the precision of the test increases slightly, resulting in a constraint on the signal amplitude of $A = 1.05_{-0.21}^{+0.25}$, where $A = 1$ corresponds to our fiducial model. Equivalently, we report an 11% measurement of the product of the growth rate and amplitude of mass fluctuations evaluated at $z_\text{eff} = 0.02$, $f \sigma_8 = 0.428_{-0.045}^{+0.048}$, valid for our fiducial $\Lambda$CDM model. We explore the robustness of the results to a number of conceivable variations in the analysis and find that individual variations shift the preferred signal amplitude by less than ${\sim}0.5\sigma$. We briefly discuss our Supercal SN Ia results in comparison with our previous results using the JLA compilation.
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DES Y3 3x2pt analysis constrains S8=0.776±0.017 and Ωm=0.339±0.032 in flat ΛCDM, consistent with Planck CMB results at p=0.13-0.48.
SN peculiar velocities combined with Planck CMB yield simultaneous constraints on σ8, γ and Ωk, with ~2σ preference for positive curvature and GR-consistent growth.
Full-GR simulations find that inhomogeneous curvature produces only sub-dominant systematic offsets in growth-rate measurements from magnitude fluctuations at z ≲ 0.2 relative to current statistical errors.
Final Planck CMB data confirms the flat 6-parameter ΛCDM model with Ω_c h² = 0.120 ± 0.001, Ω_b h² = 0.0224 ± 0.0001, n_s = 0.965 ± 0.004, τ = 0.054 ± 0.007, H_0 = 67.4 ± 0.5 km/s/Mpc, and no strong evidence for extensions.
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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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Tracing Signatures of Modified Gravity in Redshift-Space Galaxy Bispectrum Multipoles: Prospects for Euclid
In Hu-Sawicki f(R) gravity the redshift-space bispectrum monopole and quadrupole show 2-8% deviations from GR at z=0.7 and k~0.3 h/Mpc with forecasted SNR of 30 and 15 for Euclid.
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Dark Energy Survey Year 3 Results: Cosmological Constraints from Galaxy Clustering and Weak Lensing
DES Y3 3x2pt analysis constrains S8=0.776±0.017 and Ωm=0.339±0.032 in flat ΛCDM, consistent with Planck CMB results at p=0.13-0.48.
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Joint Curvature and Growth Rate measurements with Supernova Peculiar Velocities and the CMB
SN peculiar velocities combined with Planck CMB yield simultaneous constraints on σ8, γ and Ωk, with ~2σ preference for positive curvature and GR-consistent growth.
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Impact of inhomogeneous curvature on growth rate measurements from magnitude fluctuations
Full-GR simulations find that inhomogeneous curvature produces only sub-dominant systematic offsets in growth-rate measurements from magnitude fluctuations at z ≲ 0.2 relative to current statistical errors.
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Planck 2018 results. VI. Cosmological parameters
Final Planck CMB data confirms the flat 6-parameter ΛCDM model with Ω_c h² = 0.120 ± 0.001, Ω_b h² = 0.0224 ± 0.0001, n_s = 0.965 ± 0.004, τ = 0.054 ± 0.007, H_0 = 67.4 ± 0.5 km/s/Mpc, and no strong evidence for extensions.