Editing Critical phenomena (section)

==Mathematical tools==

The main mathematical tools to study critical points are [[renormalization group]], which takes advantage of the Russian dolls picture or the [[self-similarity]] to explain universality and predict numerically the critical exponents, and [[variational perturbation theory]], which converts divergent perturbation expansions into convergent strong-coupling expansions relevant to critical phenomena. In two-dimensional systems, [[conformal field theory]] is a powerful tool which has discovered many new properties of 2D critical systems, employing the fact that scale invariance, along with a few other requisites, leads to an infinite [[symmetry group]].