phase transition

Syllable breakdown

Dictionary meaning

In complexity science, a sudden, qualitative change in the macroscopic behaviour of a system as a control parameter crosses a critical threshold; analogous to water freezing or boiling, but applied to social, biological, neural, or economic systems; often associated with bifurcation points and critical phenomena

History and origin

Originally from thermodynamics (solid/liquid/gas transitions); extended to complex systems by physicists studying criticality; the use in social and cognitive science became widespread from the 1990s

Examples

• The transition from individual foraging to coordinated column behaviour in ants is a phase transition driven by pheromone concentration.
• Percolation theory describes a phase transition in connectivity: below a critical density, a network is fragmented; above it, a giant connected cluster suddenly forms.

Synonyms: critical transition, tipping point (informal), bifurcation (overlap)