The Equilibrium Ladder
The assumption of equilibrium is not a monolithic concept; rather, it is a hierarchy of approximations. A robust network must distinguish between these levels to apply the most efficient and physically appropriate model. Hover over each level to explore its role.
Level 5: Nuclear Statistical Equilibrium (NSE)
The highest level of equilibrium. All strong/EM reactions are balanced. Composition is set by T, ρ, and \(Y_e\).
Level 4: Global QSE
A single large group of heavy nuclei is in equilibrium, but the total number of heavy nuclei (\\(Y_h\\)) is kinetically controlled. Classic case: alpha-rich freeze-out.
Level 3: QSE Clusters
Distinct groups (e.g., Si-group, Fe-group) are internally equilibrated, but not with each other. Governed by slow reactions linking the clusters.
Level 2: Partial Equilibrium
A single species with a very short lifetime is assumed to be in equilibrium with its production and destruction channels. Classic example: Deuterium (H-2).
Level 1: Full Kinetic Network
The most general state where no equilibrium is assumed. The full system of ODEs is solved, which is always valid but computationally expensive.
Select a Level
Hover over a level on the ladder to learn more about its role in nuclear reaction networks.
QSE Criteria Dashboard
Translating the physical framework of QSE into a functional algorithm requires a set of practical, implementable rules. Here, we investigate the primary criteria used to establish and break equilibrium.
Astrophysical Scenarios
The general principles of QSE must be adapted to the unique physical conditions of different stellar environments. A number of complicating factors prevent a one-size-fits-all approach.
GridFire: Current State & Validation
A robust QSE network requires more than just physical rules; it needs careful numerical implementation. The following checklist summarizes the key features of a reliable code, many of which are targets for the GridFire project.