Relativistic field equations are time-symmetric and permit both retarded and advanced contributions, yet cosmology typically enforces retarded behavior by boundary condition rather than dynamical necessity. This work develops a dual-sector framework in which advanced-looking effects arise as projections of σ-ordered spacelike dynamics into the τ-foliation, rather than from retrocausal signaling. Ordinary matter evolves along timelike trajectories parameterized by proper time τ, while a σ-sector evolves along spacelike worldlines under an invariant parameter σ. The coexistence of distinct evolution parameters allows spacelike kinematic contributions to contribute to the effective cosmological background without requiring modifications to general relativity or the introduction of additional metric structure. A minimal stress–energy formulation shows that, once the σ-sector approaches a statistically homogeneous state, it appears as a smooth, non-clustering background component with an effective equation-of-state parameter approaching minus one, arising from Lorentz-invariant spacelike kinematics and projection effects rather than scalar potentials, negative masses, or exotic interactions. Dynamically negligible at early times and increasingly relevant as ordinary matter dilutes, the σ-sector offers a structural explanation for late-time cosmic acceleration consistent with observed large-scale homogeneity. This framework suggests that cosmic acceleration may reflect the geometry of dual temporal foliations rather than a distinct dark-energy substance.
V. Petri (Fri,) studied this question.