Testing Low-Redshift Cosmic Acceleration with Large-Scale Structure.

Area of Science:

• Cosmology
• Astrophysics
• Particle Physics

Background:

• The universe's expansion is accelerating, driven by dark energy.
• Baryon acoustic oscillations (BAO) provide a standard ruler to measure cosmic distances.
• Galaxy void-galaxy correlations offer an independent probe of large-scale structure and cosmic acceleration.

Purpose of the Study:

• To investigate the cosmological implications of void-galaxy cross-correlation measurements.
• To independently confirm late-time cosmic acceleration attributed to dark energy.
• To measure the Hubble constant and constrain the dark energy equation of state.

Main Methods:

• Analyzing void-galaxy cross-correlation data at redshift z=0.57.
• Combining void data with baryon acoustic oscillation (BAO) measurements across a range of redshifts (0.1
• Utilizing a nucleosynthesis prior on Ωbh² for Hubble constant calculations.

Main Results:

• Direct evidence for late-time cosmic acceleration from dark energy at >10σ significance, independent of CMB and supernovae data.
• Hubble constant measurements: H₀=72.3±1.9 km s⁻¹ Mpc⁻¹ (BAO+voids, z<2) and H₀=69.0±1.2 km s⁻¹ Mpc⁻¹ (adding Lyman-α BAO, z=2.34), both independent of CMB.
• Improved measurement of the dark energy equation of state by >40% when adding void data to existing cosmological datasets.

Conclusions:

• Void-galaxy correlations provide robust, independent evidence for dark energy and cosmic acceleration.
• The measurements are consistent with the standard flat ΛCDM model.
• This research enhances our understanding of dark energy's role in the universe's evolution.