Phenomenology

Matter Coupling

A theory of gravity is incomplete until it says how matter couples to geometry. The minimal coupling principle of General Relativity is a statement about the universality of geometry. If Hypothesis B is correct, there should be an analogous principle for closed-string gravity.

This question is not merely formal. The coupling determines what matter sees, which trajectories are natural, which wave equations are physical, and what phenomena can distinguish the theory from its Riemannian sectors.

Phenomenology

The working hypothesis must lead to physics. Phenomenology enters when the theory is asked to describe situations in which closed-string gravitational structure may leave an imprint beyond an ordinary Riemannian approximation.

Possible arenas include weak-field gravity, post-Newtonian limits, cosmology, compact objects, wormhole geometries, and gravitational waves. In this Research Program, gravitational waves are also treated as part of the broader propagation problem.

The purpose is not to force deviations from General Relativity. The purpose is to identify which predictions follow from the proposed geometry, whether they are compatible with observation, and whether the theory can be falsified.

Physical Tests

The theory must face observation. It must make contact with solar-system gravity, cosmology, black holes, gravitational waves, and any future regime in which closed-string gravitational effects can be constrained.

Search phrases such as post-Newtonian string gravity, cosmology possibly without a dark sector, and stringy gravity name possible test arenas. They do not by themselves establish a result. They indicate where the working hypothesis can become testable.