Quantum Field Theory Implications of the Emergent Causal Time Field

Building on the causal-Machian emergent time theory {Jaster2026a} and its Planck-scale regularisation {Jaster2026b}, we examine the implications for quantum field theory in an exploratory and phenomenological spirit. All field actions are evaluated on the physical clock metric ĝμν; the factor √Θ in the Lagrangian density follows from the identity √-ĝ=√-q·√Θ and is geometrically derived. We work in signature $(-,+,+,+)$ with the convention L⊃-1/2ĝμν∂_μφ\, ∂_νφ. Throughout the paper Θ is treated as a fixed semiclassical background in the fixed-Θ approximation; the self-consistent variation generates non-local additional terms and is an open task. Two variants are analysed. In the base model a single cosmological causal field Θ≈1 governs all current-epoch physics; all Standard Model predictions that depend only on the local metric are reproduced to the precision of 1-Θ≈ e^-10⁶⁰ (preferred-frame effects from UH^μ are not included in this estimate). In the scale-separation model Θ=Θcosm·Θloc, a local causal field Θloc at the scale mloc⁻¹ is introduced as an approximation valid to O(HEW/mH)~10⁻¹⁷ and may provide candidate ingredients for a modified electroweak phase transition and for the Sakharov conditions; quantitative predictions require calculations not yet performed. The scale-separation model introduces no new dimensionful parameter, but a dimensionless coupling ζ (Section 3.3) remains undetermined. The scalar Θ is a semiclassical constraint functional requiring no independent quantisation within the present framework.