Late-time cosmology and structure formation in quadratic f(Q) gravity
Document Type
Article
Publication Date
7-2026
Abstract
We study the cosmological dynamics of the quadratic symmetric teleparallel gravity model f(Q)=Q+αQ2+β, which introduces an H 4 correction to the Friedmann equation due to Q ∝ H 2. Using the exact algebraic solution for H (z), we reconstruct the effective dark-energy sector and compare the background evolution with ΛCDM using Type Ia supernovae, BAO, and cosmic-chronometer data. At the perturbative level, the model modifies the Poisson equation through a time-dependent effective gravitational coupling Geff(z)=G[1+23AE2(z)]−1, where A=18αH02. For α ' 0 this produces a weakened gravitational interaction, suppressing the linear growth factor D (z), the growth rate f (z), and the RSD observable fσ 8(z). In the nonlinear regime, the reduced gravitational strength increases the spherical-collapse threshold and suppresses the halo mass function, leading to a lower predicted value of S8=σ8Ωm/0.3. Thus, the quadratic f (Q) extension can reproduce mild deviations from ΛCDM at the background level while naturally alleviating the S 8 tension, offering a viable modified-gravity explanation for recent observational hints of dynamical dark energy.
Recommended Citation
Nashed, Gamal; Tretyakov, P V.; and Eid, A, "Late-time cosmology and structure formation in quadratic f(Q) gravity" (2026). Centre for Theoretical Physics and Computations. 399.
https://buescholar.bue.edu.eg/centre_theoretical_physics/399