"book-pflow-xyz/chapters/appendix-d-glossary.md" . . "Stochastic Differential Equation"@en . "Here, specifically the chemical Langevin equation: continuous state evolving under the same propensities SSA uses, but with intrinsic firing noise built into the diffusion term rather than sampled as discrete events. Cheap to sweep like the ODE, with an honest variance band like SSA — the regime between them. Distinct from a layer of exogenous Brownian motion added to an ODE for external uncertainty (a price feed, say), which answers a different question (Chapter 3)."@en . . "SDE"@en . "3"^^ .