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Background and perturbation constraints on power-law and exponential f(G) gravity models from recent cosmological observations
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DOI：10.1016/j.dark.2026.102370.png)
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Abstract
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In the present paper, we constrain the modified Gauss-Bonnet gravity models by at both background and perturbation levels, using different observational data sets. We first apply the cosmic chronometers (CC), Supernova type Ia (PP), and DESI BAO data sets on the first Friedmann equation (Hubble parameter) obtained using two different f(G) models to get (Ωm, H0, β and p). Then we apply the Redshift Space distortion (RSD) data to structure growth equation to study its implication on large-scale structure. This helps to get the additional (σ8) parameter for each model. In both cases we use both MCMC and statistical analysis to get the best fit parameters. The cosmological implications of the considered models are investigated in a flat, homogeneous, isotropic Friedmann-Robert-Walker (FRW) geometry and the case of quasi-Newtonian space time for structure grow equation. Comparative analysis with the ΛCDM model are carried out and observational implications of the considered f(G) models are discussed in detail. The analysis is performed using three dataset combinations: (i) CC+PP, (ii) CC+PP+RSD and iii) CC+PP+RSD+DESI BAO. The modified Friedmann and perturbation equations are solved numerically for two functional forms of f(G) gravity, namely the power-law and exponential models. The cosmological parameters are constrained through Markov Chain Monte Carlo (MCMC) simulations. To evaluate the statistical performance of the models, we compute the corrected Akaike Information Criterion (AICc), the Deviance Information Criterion (DIC) and the Bayesian Information Criterion (BIC). The present best fits Hubble, matter desnity and σ8 parameters are H0=70.0972±2.8926 , Ωm=0.2981±0.0606 and σ8=0.8112±0.0557 for the power-law f(G) model and H0=69.6041±2.9220 , Ωm=0.3106±0.0559 and σ8=0.8007±0.0557 for the exponential model, which may alleviate the Hubble and σ8 tensions. Our results show that both f(G) models provide background and perturbation evolutions consistent with current observational data. In addition, the exponential model predicts a transitional feature, transition from accelerated to decelerated expansion at z ≈ 0.63, whereas the power-law model exhibits the transitional redshift at z ≈ 0.65.
Keywords:
f(G) gravity
Perturbation
Power law of f(G)
Data analysis
Deceleration parameter
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