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Critical phenomena
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Fluctuations and universality near critical points.
Near a critical point, correlation length diverges, and quantities follow power laws with universal exponents shared by very different systems (universality).
Water-steam and a magnet behave similarly at their critical points.
Described by the renormalisation group.
In more detail
Critical phenomena occur near a phase transition, where fluctuations become large and properties follow power laws. Different systems share the same critical exponents, which defines universality classes.
Real-world uses
- Critical phenomena explain why very different systems behave similarly near transitions.
- Physicists use scaling ideas to study fluids and magnets.
- Physicists study critical phenomena near phase transitions, where fluctuations occur on all length scales.
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Frequently asked questions
What is universality?
The idea that different systems share critical exponents if they have the same symmetry and dimension.
What happens at the critical point?
Correlation lengths diverge and the system shows scale-free fluctuations.
What is universality?
The idea that very different systems show the same behaviour near their critical points, so their critical exponents match.