MCMC Analysis of f(G) Gravity Yields H0=64.02 km/s/Mpc and Favors LambdaCDM
MCMC constraints on two viable f(G) models using four cosmological probes show that LambdaCDM remains statistically preferred. Model II returns a lower H0 and Omega_m0 once DESI BAO enters the fit. Linear growth remains compatible with RSD observations but the models are not favored over baseline cosmology.
The analysis employs an ensemble MCMC sampler on cumulative datasets to bound both background expansion and sub-horizon growth for an arctangent and a generalized power-law f(G) form. Inclusion of the Year-1 DESI BAO measurements drives a clear downward shift in preferred H0 and Omega_m0 relative to earlier compilations, while both models remain linearly stable and produce late-time transition redshifts near z=0.5-0.6.
These numerical results align with the broader pattern seen in DESI BAO analyses of dynamical dark energy, where extra degrees of freedom in modified gravity are penalized once geometric and growth observables are combined. The modest information criteria differences indicate that current data lack the leverage to distinguish f(G) from LambdaCDM at high significance, echoing earlier Planck-plus-BAO tensions on the same parameter plane.
Next-generation DESI releases and Euclid weak-lensing spectra will tighten growth-index constraints by roughly a factor of two within three years, offering a decisive test of whether the reported stability persists under higher-precision perturbation data.
DESI collaboration: Year-3 BAO plus full-shape data will push the f(G) growth-index posterior width below 0.03 within 24 months or exclude both models at >3 sigma.
Sources (2)
- [1]Primary Source(https://arxiv.org/abs/2609.16037)
- [2]Supporting Source(https://arxiv.org/abs/2404.03002)