HDG_XL: Temporal Memory Suppression of Late-Time Structure Growth — Code and Data

This repository contains the complete numerical implementation, data, and analysis pipeline for the paper "History-Dependent Gravity: Temporal Memory Suppression of Late-Time Structure Growth". History-Dependent Gravity (HDG) is a modified gravity framework based on nonlocal temporal memory effects characterized by a spectral density ρ(μ). In the critical regime ρ(μ) = const, the theory develops a marginal infrared fixed point leading to logarithmic suppression of structure growth: δ(a) ∝ [ln(a/a*)]². The repository includes:• Core HDG module (hdg_core.py) with growth equation solver• 2D and 3D Metropolis-Hastings MCMC samplers• Robustness tests (profile likelihood, Planck-fixed σ₈, Ω_m variation)• Publication-quality figure generators• Low-redshift fσ₈ data compilation (6dFGS, BOSS, DES, eBOSS) Key results:• Transition scale: a* = 0.165 (+0.234, -0.096) [68% C.L.]• σ₈ = 0.784 (+0.122, -0.104)• Ω_m = 0.274 (+0.067, -0.048)• χ² improvement vs Planck-fixed ΛCDM: Δχ² ≈ 54.8 The code is fully reproducible and can be used to test HDG predictions against additional datasets or extend the analysis with covariance matrices and joint CMB+BAO+weak lensing inference. Companion paper: arXiv:XXXX.XXXXX (to be updated after arXiv submission)