Completing General Relativity: Dark Energy as a Fossil Field from Physical Information

For a century, the cosmological constant Λ—the standard placeholder for dark energy—has described cosmic acceleration without physical identity. The Dark Energy Spectroscopic Instrument (DESI) now reports that dark energy is diluting—its equation of state w(z) evolves and crosses w = −1. No model answers: What is dark energy? Why does positive energy—which General Relativity says attracts—appear to repel (driving the accelerating expansion of the universe)? We answer from a first principle: Physical Information. The universe emerges via two conservative phase transitions. Within this framework, dark energy is identified as the untransformed remnant of the primordial positive-energy domain—a fossil field from cosmic genesis. This ontology yields a power-law decay: ρDE ∝ a2−n (where a2 is the background scale factor, 0 < n < 2), directly predicting that dark energy slowly dilutes over cosmic time—a behavior qualitatively matching the DESI observation. The same ontology resolves the “repulsive gravity” paradox: cosmic acceleration is a thermodynamic response—our universe expands to balance the diluting fossil field, as a balloon expands in falling pressure. Far from conflicting with General Relativity, the framework completes it—giving Λ a physical identity: the local density of this fossil field. The same causal architecture also turns the cosmic coincidence (ρm/ρDE ∼ 1 today) into a natural outcome of stable coupled dynamics. Its central prediction—a power-law decay ρDE ∝ a2−n with 0 < n < 2—is testable with upcoming surveys (Euclid, Rubin) and distinguishes it from Λ and all scalar field models. This work transforms dark energy from a fitting parameter into a derived property of cosmic genesis: a new, testable paradigm rooted in first principles.