Fig 4. Geodesic boundary leads to the Quasi-Steady-State Approximation.

By promoting the initial conditions E₀ and S₀ to parameters, the geodesics reveal yet another limiting approximation. Similar to Figs 2 and 3, the boundary is reached just before τ ≈ 2 (top). Bottom left: the final parameter space velocities (v₁ ∼ log k_f, v₂ ∼ log k_r v₃ ∼ log E₀, and v₄ ∼ log S₀) indicate that the limit corresponds to two parameters becoming infinite and a third becoming zero. Bottom right: the smallest FIM eigenvalue becomes zero at the manifold boundary.