Directional Anisotropy Gravity: A Research Invitation (v3)

This document has one purpose: to explain, in plain language, why Directional Anisotropy Gravity is a research programme worth pursuing — what it is trying to say about the structure of reality, what it has already established, what remains to be proved, and what observations could confirm or refute it. It is written for physicists who have not read the technical papers, for mathematicians who might contribute to the open problems, and for anyone curious about what it would mean if space itself were made of something — something discrete, oriented, and capable of memory. The theory is developed at two levels. The gravitational sector is built on one idea: the vacuum is the state of maximum directional entropy. The substrate sector is built on a complementary idea: neighbouring substrate nodes exchange directional information, with the exchange preferring the direction of the connecting bond — direction-orbit coupling, as simple in conception as spin-orbit coupling in atomic physics, and as consequential. A conjectural extension toward a unified description of gravity, dark sector, and Standard Model gauge structure is outlined as a research programme, with open steps stated explicitly. Current quantitative results include: both post-Newtonian parameters derived from first principles (γPPN = βPPN = 1, consistent with the Cassini bound); a two-parameter memory-halo model fitted to 152 SPARC rotation curves (LSB median χ²/ν = 1.02); and a background expansion history consistent with DESI DR1 BAO data (χ²/ν = 1.25 vs 1.54 for Planck-2018 ΛCDM). Several open mathematical steps remain. Where a result is a conjecture or exploratory estimate, this is stated explicitly. Companion documents: DAG gravity sector, v11: 10.5281/zenodo.19389365 DAG substrate sector, v11: 10.5281/zenodo.19473405 DAG gauge-structure programme, v1: 10.5281/zenodo.19614270 DAG technical supplement: 10.5281/zenodo.19683210 βPPN = 1 derivation: 10.5281/zenodo.19597451 FRW perturbations: 10.5281/zenodo.19605779