The Informational Dark Sector: A Damkohler-Regulated Scalar Field That Recovers LCDM and Reproduces the Cosmological Constant

We present GUBIM (Grand Unified Brane-Informational Model), an effective kinetic framework in which dark matter and dark energy emerge as two regimes of a single informational scalar field Phi, differentiated by the cosmological Damkohler number Re -- the ratio of the informational reaction rate to the Hubble expansion rate. The dark-sector coupling is obtained from the Boltzmann collision integral with a Breit-Wigner cross-section, yielding Q = 3H rhoₜot epsilonₘ epsilonDE / (1 + Re²). This bimolecular interaction exhibits Le Chatelier saturation: at high Re (early universe), Q -> 0 and the background equation of state approaches w -> -1, recovering LCDM automatically. The dark-matter-like phenomenology at galactic scales arises from the perturbative clustering of Phi, not from the background w (z). LCDM was not assumed; it emerges as the Re -> infinity limit. Validation against 1094 data points (cosmic chronometers, Pantheon+ SNIa, DESI BAO, CMB distance priors) yields a statistical tie with LCDM (Delta chi² = -2. 63, Delta AIC = -0. 63). Full CAMB integration produces CMB power spectrum deviations below 1. 63% at all multipoles. The background growth suppression gives sigma₈ (GUBIM) /sigma₈ (LCDM) = 0. 989 (1. 1% suppression), placing GUBIM in the direction favored by weak-lensing surveys. Gravitational waves propagate at cT = c exactly. The framework offers candidate explanations for features that LCDM treats as free inputs: (1) rhoLambda predicted to 0. 23% via Landauer erasure at the Hubble horizon; (2) w ~ -1 from near-complete informational equilibration; (3) a common origin for dark matter and dark energy (one field, different Re regimes) ; (4) Milgrom's a₀ derived to 0. 22% as a₀ = c H₀ sqrt (4/3) / (2 pi) ; (5) the coupling constant alpha₀ = 7. 71 derived from Verlinde-Zurek modular fluctuations to 0. 81%; (6) a geometric slow-roll bound that DESI DR1 violates and LCDM satisfies only trivially. Testable prediction: w₀ = -0. 941 +/- 0. 03 for Euclid/DESI DR3. This version supersedes v5 ("Dark Matter as a Dissipative Informational Condensate"). Major additions: Boltzmann-derived Q interaction, Gamma₀ = 1/H resolution, multi-catalog SNIa analysis (Pantheon+/DES/Union3/JLA), CAMB sigma₈ benchmark, holographic Q derivation, MOND derivation (companion paper), Verlinde-Zurek alpha₀ derivation (companion paper), theory status table.