Clearance

Definition (canon)

Removal of a species from a pool, and the competing exit against which any gate's throughput is read.

Four kinds, and only the first crosses a compartment edge: transport out (mass crosses an edge); conversion in place (identity changes, mass stays); dilution (no agent acts and the denominator grows); sequestration (the species remains but is made unavailable, by deepening a well). The first two are rates and enter as drift. Dilution rescales the coordinate and sequestration changes the barrier itself, so neither is a force on the state.

With dwell-before-removal trel and attempt time τ₀, a species stays behind a barrier only where ΔV > D ln(trel/τ₀). With no clearance no barrier is high enough and no edge is selective.

In plain words

How things get taken out. What a gate does is always read against the other ways out.

It is not

• Always a neighbouring compartment pulling. That holds only for the first kind.

What would defeat it

• Follows from the definition. A system where adding or removing an exit changes nothing about throughput through the gate.