Fisher renormalisation and conformal field theory

The “Fisher renormalisation” of critical exponents, caused by addition of constrained annealing “hidden variables” to a system, is investigated within conformal field theory. The standard unitary SU (2) conformal field theory does not allow for Fisher renormalisation, and extended unitary conformal field theories are instead investigated. These are provided by explicit constructions based on coupling the energy operator to new degrees of freedom in a conformally invariant way. They lead to new families of generalised model including Fisher-renormalised exponents or new renormalisations.