The Holographic Entropic Arrow: Time as Information Saturation and the Impossibility of Retrocausality

This paper presents a new physical framework proving the impossibility of backward time travel based on holographic information saturation. We introduce a dimensionless entropic saturation parameter χ(t) ≡ S_matter(t) / S_H(t) that monotonically increases from 0 to 1. The direction of time is defined as dχ/dt > 0. Key results: 1. Retrocausality is physically impossible because it requires erasing information from the cosmological horizon. 2. "Time acceleration" is explained as higher local information processing rate Γ relative to cosmic background. 3. The model predicts cosmic expansion will halt and reverse in 31.4 ± 2.3 Gyr at χ=1. This work provides the dynamical engine unifying four prior theories: Equilibrium Expansion, Virgin Wave, 120-Zero Solution, and the Reader-Light Principle. Part 6 of the HERC Framework: Holographic Equilibrium & Reversal Cosmology. This theory is falsifiable within 10 years by Euclid and DESI.