Time as Actualization: A foundational ontology reconciling the quantum future and the relativistic past

Time–Actualization (TA) is a foundational ontology for physics built on a single move: quantum mechanics describes the potential future, general relativity describes the actualized past, and the present is the process of actualization that converts the former into the latter. The ontology is a minimal triplet (ρ, ν, ⟨P,≺⟩): a positive normalized state ρ on a local net of algebras (the conditional future potential), a primitive tempo ν (the rate of becoming), and a growing causal set ⟨P,≺⟩ (the past). TA assumes the quantum formalism and the relativistic causal structure as imported building blocks; it does not attempt to derive the Born rule, Einstein's equations, or the constants. From eight core hypotheses we obtain: a structural arrow of time prior to thermodynamics (D1); the dissolution of the measurement problem (D2), the EPR paradox (D3) and the superluminal-signalling worry (D4); a causally determined preferred basis (D5) — the actualization basis is einselected by the event's causal past, rather than posited; a thermodynamic arrow via Landauer–Jaynes–Spohn (D6); and a conditional coherence lemma showing the actualization dynamics is generally covariant and Bell-causal once the substrate carries the standard locality of physics (D7). Measurement, becoming, and causal-set growth are one process. TA is empirically equivalent to (quantum mechanics + a causal-set substrate): it makes no distinctive prediction, its only signature being the generic causal-set swerve inherited from discreteness. Its contribution is ontological clarity and a unifying reading, not a new number. The three problems it leaves open — the relativistic actualization dynamics, the continuum limit (Hauptvermutung), and the Born rule — are, by construction, not TA's to close. Version 2 (June 2026). This version adds a section, “The physics of the tempo ν”, developing TA’s only non-imported primitive: a no-new-constant saturation law (ν pinned to the energy uncertainty ΔE), an emergent invariant proper time Σν−1, the unification of special- and general-relativistic time dilation as the redshift of ΔE, and the closure of the signature question (TA is empirically quantum mechanics; CSL/GRW and Diósi–Penrose are excluded). All Tier-2 consistency and ontology, empirically silent. Minor consistency fixes. The concept DOI is unchanged.