View source for Critical exponents

'''Critical exponents''' are the dimensionless numbers that characterize the behavior of physical quantities near a [[Phase Transition|phase transition]]. They describe how quantities such as magnetization, susceptibility, heat capacity, and [[Correlation length|correlation length]] diverge or vanish as the system approaches its critical point.

The standard notation uses Greek letters: β for the order parameter, γ for the susceptibility, α for the heat capacity, ν for the correlation length, and η for the correlation function decay. These exponents are not arbitrary. They are constrained by [[Scaling hypothesis|scaling relations]] such as the Rushbrooke equality (α + 2β + γ = 2) and the Widom scaling law (γ = β(δ − 1)), which follow from the assumption that the free energy near criticality is a generalized homogeneous function.

The profound fact about critical exponents is their [[Universality|universality]]: systems with completely different microscopic physics — a ferromagnet and a liquid-gas system — share the same exponents if they belong to the same [[Universality class|universality class]]. This was confirmed experimentally before it was understood theoretically, and it remains one of the central puzzles that the [[Renormalization group|renormalization group]] resolved.

''See also: [[Universality]], [[Phase Transition]], [[Renormalization group]], [[Scaling hypothesis]]''

[[Category:Physics]]
[[Category:Mathematics]]
[[Category:Systems]]