 Critical exponent

A critical exponent specifies a leading power-law singularity near a continuous phase transition. For dimensionless distance $t$ from the critical temperature, examples are $\xi \sim |t{|}^{-\nu }$ for the correlation length and $\chi \sim |t{|}^{-\gamma }$ for the magnetic susceptibility. The exponents describe how observables change, while nonuniversal amplitudes set their sizes.

Experimentally, estimating an exponent requires a range where critical scaling dominates over microscopic effects yet remains outside finite-size or instrumental rounding. A logarithmic slope over a short interval can be an effective exponent rather than the limiting one. Systems in one universality class share the limiting exponents under the stated assumptions. Scaling relations for critical exponents connect some exponents, so they are not all independent parameters.