Void Edge Sharpness

Observations of cosmic voids reveal that many large voids have remarkably sharp edges — the transition from the underdense void interior to the surrounding overdense wall occurs over a smaller physical scale than ΛCDM's gravitational collapse models predict. In the standard model, void walls form as matter flows outward under gravitational pressure from the overdense surroundings while simultaneously being pulled by the surrounding matter distribution; this process produces a relatively gradual transition with a scale set by the nonlinear collapse radius. Successive Collision Theory attributes sharp void edges to the physical mechanism of collision-front compression: matter was swept into the wall layer by the collision front passing at a specific velocity, producing a compressed layer whose thickness is set by the collision dynamics rather than by slow gravitational drainage. The original swept shell retains a sharp physical boundary that is further sharpened by subsequent self-gravitational collapse of the shell material.

The angular momentum inherited by material within the void wall provides additional sharpening. As material flows along the wall surface under gravity, it follows trajectories that are constrained by the angular momentum barrier perpendicular to the wall plane. This means matter cannot easily cross the wall boundary in either direction: it is gravitationally bound within the wall layer by the perpendicular angular momentum component. The wall therefore acts as a one-way ratchet during initial formation — swept material deposits into the layer and is then held there by the angular momentum barrier — producing and maintaining a sharper boundary than pure gravitational dynamics would generate. Void edge sharpness is thus a combined measure of the collision front's compression efficiency and the angular momentum deposition per unit area, making it a quantitative probe of the original collision parameters.