The previous chapter introduced Occupancy as the mechanism that allows an Identity to move through a stationary lattice. However, another fundamental question immediately follows.
If an Identity occupies a lattice node, why should it ever leave that node? What determines when movement begins, and why does it occur in one direction rather than another?
The REM Framework answers these questions through the concept of Pressure. Pressure does not directly move an Identity. Instead, it represents the accumulated local imbalance experienced by an Occupancy as it interacts with the surrounding lattice.
Why is Pressure Necessary?
Without Pressure, movement would have to occur immediately whenever a small imbalance appears. Such behaviour would make motion extremely sensitive to tiny fluctuations and would produce unrealistic jittering as Occupancies constantly change between neighbouring nodes.
Instead, the REM Framework allows small local imbalances to accumulate over time. Only after sufficient imbalance has developed does movement become favourable. This introduces stability while preserving completely local interactions.
Pressure therefore provides the missing link between local mechanical imbalance and eventual movement.
What is Pressure?
Pressure is a persistent quantity associated with an Occupancy. It measures the accumulated directional imbalance experienced by an Identity while occupying a particular lattice node.
Unlike the instantaneous lattice gradient, Pressure does not disappear after each update. Instead, it accumulates over successive recursive updates, preserving the mechanical history of the local interaction.
This persistence allows weak influences to combine naturally over time until they become significant enough to produce movement.
Why Does Pressure Belong to the Occupancy?
Pressure is not a property of the lattice itself. Empty lattice nodes possess no transport behaviour.
Neither is Pressure purely a property of the Identity. The same Identity experiences different local conditions depending upon which node it currently occupies.
Pressure therefore belongs to the relationship between the Identity and the lattice node. It is a property of the Occupancy itself and transfers together with the Identity whenever Occupancy changes.
Measuring Local Imbalance
Each recursive update measures the local imbalance surrounding the occupied node. Neighbouring nodes influence the Occupancy differently depending upon their relative mechanical state.
These local measurements produce a directional gradient. Rather than immediately causing movement, this gradient contributes to the accumulated Pressure stored by the Occupancy.
As long as an imbalance remains, Pressure continues to increase in the corresponding direction. If the imbalance disappears, Pressure no longer increases.
Accumulation
Pressure is one of the few quantities within the REM Framework that remembers previous updates. Each measurement contributes to the existing Pressure, allowing many small influences to combine into a larger effect.
This accumulation introduces a natural form of inertia. Movement is no longer determined by a single instantaneous measurement but by the continuous mechanical history of the Occupancy.
The longer a consistent imbalance exists, the greater the accumulated Pressure becomes.
Pressure is not Motion
An important distinction within the REM Framework is that Pressure does not itself move an Identity. Pressure only represents the tendency for movement to occur.
Movement begins only when the accumulated Pressure exceeds the conditions required for an Occupancy transfer. This separation between accumulation and movement keeps the recursive dynamics stable while allowing motion to emerge naturally from local interactions.
Current Status
Within the REM Framework, Pressure is currently treated as a persistent quantity belonging to the Occupancy. It provides the mechanism by which repeated local interactions gradually build the conditions required for movement.
This approach avoids instantaneous reactions to small fluctuations while allowing motion to emerge from entirely local recursive dynamics. Future research may reveal additional emergent behaviour resulting from Pressure accumulation beyond transport alone.
Looking Forward
Pressure now provides a tendency for movement, but another question remains.
At what point should accumulated Pressure actually change an Occupancy? How is the direction of movement chosen? And how can repeated local transfers produce smooth continuous motion?
These questions lead directly to the next concept in the REM Framework: Transport.