- 03-107 Vieri Mastropietro
- Ising models with four spin interaction at criticality
Mar 12, 03
(auto. generated ps),
of related papers
Abstract. We consider two bidimensional Ising models
coupled by an interaction
quartic in the spins. The model contains both the Eight vertex
and the Ashkin Teller models for suitable values
of the parameters.
By Renormalization Group
methods we write a convergent perturbative expansion for
the specific heat and for the energy-energy
correlation up to the critical temperature.
A form of nonuniversality is proved, in the sense that
the critical behaviour is described in terms of
critical indices which are non trivial functions of the coupling.
The logarithmic singularity of the specific heat
of the Ising model is removed or changed in a power law
(with a non universal critical index)
depending on the sign of the interaction.