Matter as the Catalyst of Classical Spacetime: Why the Universe Remains Classical After the First Pruning Without Baryons, Spacetime Dissolves

We propose that baryonic matter or more generally, any entropy-concentrating structure plays a catalytic role in the Stochastic Rupture (SR) framework: it is not merelyconsistent with classicality but necessary for its ongoing maintenance. The SR pruning mechanism res when the local informational saturation eld χ = SvN/IBousso crosses the threshold η. We show quantitatively that the cosmological radiation background alone produces χ ∼ 10−38, far below any plausible η. Only locally concentrated matter stars, collapsed structures, black holes can boost χ toward threshold in specic regions, sustaining the local pruning events that maintain classical records after the primordial storm-to-pruning transition (the First Pruning). In a hypothetical universe without baryonic asymmetry, matter and antimatter would annihilate, entropy would remain diuse, local χ would never approach η, and the universe would return to the informational Many-Worlds ocean after the First Pruning. Classicality, in this picture, is a one-time event without a catalyst a crystallization that immediately begins to dissolve. The baryonic catalyst provides the ongoing local pruning events that prevent re-coherence and maintain the classical branch of spacetime. This connects SR to baryon asymmetry, structure formation, and the ultimate fate of classicality as matter disperses in the late universe.