We investigate the evolution of linear and non-linear matter perturbations within the modified scalar-tensor framework of the -field cosmology. Using fixed late-time structural coupling parameters (A 0. 25, m 3. 0, q_ 0. 15), we derive the modified growth equation for matter density perturbations () where the effective gravitational coupling G₄₅₅ (z) dynamically modulates the gravitational attraction across cosmic epochs. Numerical evaluation reveals that while the system converges identically to standard General Relativity today (G₄₅₅/G 1. 0000 at z=0), the historical presence of the cosmic damper suppresses the aggressive growth of dark matter overdensities during the structure formation era. Consequently, our simulation yields a systematic 10. 12\% reduction in the modern matter clustering amplitude, shifting the standard CDM prediction down to S₈ = 0. 7460. This value is in remarkable agreement with local weak lensing surveys (e. g. , DES, KiDS), effectively resolving the long-standing S₈ tension that plagues the standard model without fine-tuning. We present the resulting Matter Power Spectrum P (k) as a definitive observational footprint of the -field on large-scale cosmic web structures.
Josip Zencic (Sat,) studied this question.